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MEDICINE YEAR 1 > FOUNDATIONS > Flashcards

FOUNDATIONS Flashcards

1
Q

What is the composition of a cell?

A

Water - 80%
Protein - 15%
Lipid - 2.5%
Carbohydrate -1.5%
Inorganic - 1.0%

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2
Q

What is a eukaryotic cell?

A

Any cell or organism with a nucleus

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3
Q

What are the features of a eukaryotic cell?

A
  • Outer membrane.
  • Inner cytosol: solution of proteins, electrolytes
  • Cytoskeleton - determines the shape and fluidity of cell
  • Membrane bound organelles within cytosol
  • Inclusions: structures within cytoplasm which may/may not be bound by a membrane
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4
Q

What does the Plasmalemma (outer membrane) do?

A

Separates cytoplasm from outside environment

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5
Q

What is the structure of the Plasmalemma (plasma membrane) ?

A
  • Bimolecular layer of amphipathic phospholipid molecules (phospholipid bilayer)
  • Hydrophilic heads, hydrophobic tails
    • Contains integral proteins:
      exocytose (inside → outside cell) and endocytose (outside → inside cell)
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6
Q

What are 2 properties of a cell membrane?

A

Fluid & selectively permeable

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7
Q

What are organelles?

A

Small, intracellular ‘organs’ with a specific function and structural organisation - essential to life

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8
Q

What organelles are within the cytoplasm and what are their functions?

A
  • Mitochondria (energy production)
  • Rough endoplasmic reticulum - (protein synthesis)
  • Smooth endoplasmic reticulum - (cholesterol & lipid
    synthesis/detoxification)
  • Golgi apparatus - (modification & packaging of secretions)
  • Lysosomes – (hydrolytic enzymes for intracellular digestion)
  • Nucleus – (contains genetic code)
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9
Q

What are the 3 filaments of the cytoskeleton?

A
  • Microfilaments
  • Intermediate filaments
  • Microtubules
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10
Q

What are microfilaments?

A
  • later dissociate, making them very dynamic cytoskeletal elements
  • composed of the protein actin
  • 7 nm
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11
Q

What are intermediate filaments?

A
  • Bind intracellular elements together and to the plasmalemma
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12
Q

What are the different types of intermediate filaments and their location?

A

Type of Intermediate: Location/Cell Type

  • Neurofilaments: Nerve cells
  • Glial fibrillary acidic protein: Glial cells of nervous system
  • Desmin: Muscle cells
  • Cytokeratins: Epithelial cells
  • Vimentin: Mesenchymal cells
  • Filesin: Lens of the eye
  • Lamin: Nuclei of all cells
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13
Q

What are microtubules?

A
  • hollow tubule composed of 2 types of tubulin subunits, α & β in alternating array
  • originate from centrosome
    • Kinesin is an ATPase that movestoward the cell periphery.
  • Dynein is an ATPase that moves toward the cell centre: both attach and move along mtsb.
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14
Q

What is the nucleus?

A

Contains genetic code
- Enclosed by a nuclear envelope

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15
Q

What is transcribed in the nucleus?

A

mRNA and tRNA

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16
Q

What is transcribed in the nucleolus?

A

rRNA

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17
Q

What is Euchromatin?

A

DNA loosely packed and undergoing transcription

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18
Q

What is Heterochromatin?

A
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19
Q

Where are ribosomes formed?

A

Nucleolus

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20
Q

What is the structure of ribosomes?

A
  • Small subunit: binds RNA
  • Large subunit: catalyses peptide bond formation
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21
Q

What does the Nucleolus form?

A

Ribosomes

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22
Q

What is the Endoplasmic Reticulum?

A

Net like structure

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23
Q

What is the Rough Endoplasmic Reticulum and its functions?

A
  • studded with ribosomes
  • protein synthesis
  • initiation of glycoprotein formation

Cells metabolically inactive have little ER.

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24
Q

What is the Smooth Endoplasmic Reticulum and its functions?

A
  • continuous processing of proteins from RER
  • lipid synthesis
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25
Q

What is the Golgi Apparatus?

A

Flattened, membrane bound cisternae

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26
Q

What is the function of the Golgi Apparatus?

A

Transport vesicles arrive from SER; Golgi modifies and packages them - eg: adds sugars, cleaves some proteins

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27
Q

What is the Mitochondria and its function?

A
  • Oblong, cylindrical organelles
  • Power generators of the cell (generate ATP via oxidative phosphorylation and involved in the synthesis of certain lipids and proteins)
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28
Q

What is the structure of the Mitochondria?

A
  • Inner membrane: extensively folded to form cristae, which act to increase SA
  • Contain their own DNA and system for protein production
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29
Q

What are Intercellular Junctions?

A
  • Specialised membrane structures which link individual cells together into a functional unit
  • prominent in epithelia
  • 3 types
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30
Q

What are Occluding Junctions?

A
  • link cells to form diffusion barrier
  • also known as ‘tight junctions’ or ‘zonula occludens’
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31
Q

What are Anchoring Junctions?

A

Provides mechanical strength
- Adherent junctions: create network of interconnected cells via actin, ties cell together, important in tissue exposed to abrasive forces
- also termed ‘zonula
adherens’
- Desmosomes: Links submembrane intermediate filaments of adjacent cells

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32
Q

What are Communicating (Gap) Junctions?

A
  • allow movement of molecules between cells
  • Each junction is a circular patch studded with pores produced by connexon proteins found in epithelia
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33
Q

What is Junctional Complex?

A

Close association of several types of junctions found in certain epithelial tissues
- eg: ZO: zonula occludens or tight junction, ZA: zonula adherens

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34
Q

The difference between Endocytosis and Phagocytosis..?

A
  • Endo: material from the extracellular space can be incorporated into the cell. Membrane invaginates (turns inside out), fuses, and newly made endocytic vesicle buds into cell. (Exo: opposite)
  • Phago: bacteria binds to cell surface, cell engulfs it to form phagosome, binds with lysosome containing digestive enzymes
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35
Q

What is the Cell Cycle?

A

Period of time between the birth of a cell and its own division to produce 2 daughter cells

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36
Q

What are Cycling cells?

A

Cells that continue to divide regularly in definite intervals

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37
Q

What is the cell cycle divided into?

A

Mitosis and Interphase

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38
Q

What is Interphase split into?

A

G1, S phase, G2

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39
Q

What are Cyclins?

A

Proteins whose concentration increases and decreases throughout the cycle (Cyclins A,B,E)

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40
Q

What do Cyclins activate?

A

Cyclin-dependent kinases (CDKs) - act in conjunction with cyclins

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41
Q

“Cyclins and CDKs are degraded at the end of the cell cycle” - True/False?

A

TRUE

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42
Q

What is Interphase?

A

Interval between the end of mitosis and beginning of next
- Cell is either resting or performing its specialised work not in mitosis

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43
Q

What happens during S phase?

A

DNA replication
- promoted by cyclin A and CDKs
- Begins 8hrs after mitosis… 7 to 8 hours to complete

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44
Q

What is DNA replication?

A

When the double-stranded DNA unwinds, each single strand serves as a template for creating a new matching strand.

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45
Q

“DNA can be damaged during replication and repair mechanisms exist
“ - True/False?

A

TRUE

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46
Q

Can defects in repair mechanisms cause disease?

A

YES

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47
Q

What is Xeroderma Pigmentosum?

A

Condition with defective DNA repair due to a deficiency in the “nicking endonuclease” enzyme.

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48
Q

What causes DNA damage in Xeroderma Pigmentosum?

A

UV irradiation

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49
Q

What are the clinical features of Xeroderma Pigmentosum?

A
  • dry keratosis
    hyperpigmentation
  • skin atrophy
  • increased UV sensitivity
  • potential for corneal ulcers.
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50
Q

What is a significant complication of Xeroderma Pigmentosum?

A

Risk of developing squamous cell carcinoma of the skin.

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51
Q

What is the defining step of homologous recombination (HR) in DNA repair?

A

Homologous strand exchange directed by the RAD51 protein.

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52
Q

What is the role of BRCA1 and BRCA2 in DNA repair?

A

Hereditary breast cancer suppressors

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53
Q

What is the primary genetic defect associated with Hereditary Nonpolyposis Colon Cancer (HNPCC)?

A

Mutations in the hMSH2 gene, which is responsible for mismatch repair.

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54
Q

Where is the hMSH2 gene located on the chromosome?

A

Chromosome 2.

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55
Q

What happens during G1?

A

Gap between end of mitosis and beginning of S phase
- Growth phase - initiate another cycle
- controlled by cyclin E and CDKs
- longest phase

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56
Q

At the end of G1…?

A

DNA damage results in apoptosis or G0

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57
Q

What happens in G0?

A

Contain cells that retain capacity for division and in process of differentiation but are no longer dividing
- growth factors can stimulate quiescent cells to leave G0 and re-enter the cell cycle

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58
Q

What happens during G2?

A

Gap between the end of S phase and beginning of mitosis
- Cell must duplicate organelles
- controlled by cyclin B and CDKs
- 2-4 hours to complete

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59
Q

“During interphase, the nucleus of the cell possesses a nuclear envelope a network of chromatin threads or granules and a nucleolus” - True/False

A

TRUE

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60
Q

What does Mitosis result in?

A

Distribution of identical copies of the parent cell genome to the two daughter cells

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61
Q

What are the 4 phases of Mitosis?

A
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
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62
Q

What happens during Prophase?

A
  • Nuclear membrane disintergrates, chromosomes condense
  • Centrosomes migrate to opposite sides
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63
Q

What is PROmetaphase?

A
  • Nuclear membrane and nucleolus disappear.
  • Chromosomes are entangled in a meshwork of continuous microtubules.
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64
Q

What happens during Metaphase?

A
  • Chromosomes align at metaphase plate and attach to spindle fibres
  • Colchicine arrests cell division preventing formation of microtubules of the spindle
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65
Q

What happens during Anaphase?

A
  • Spindle fibres contract, each pair of newly formed chromosomes separates and migrates to the opposite pole of spindle.
    2 identical and complete chromosomes are formed.
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66
Q

What is Non-Dysjunction?

A

Chromosomes fail to migrate properly in Ana: one daughter cell receives extra chromosomes and the other is deficient

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67
Q

What is Isochromosome?

A

2 daughter cells of unequal length due to centromere splitting transversely instead of longitudinally

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68
Q

What happens during Telophase (in progress)?

A

New nuclear membrane and nucleolus appears

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69
Q

What happens during Telophase (complete)?

A

Cytoplasm divides and two complete cells are formed

Cytokinesis: cleavage furrow develops around the equator region and daughter cells separate

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70
Q

What are daughter cells able to do after mitosis?

A
  • Enter the cell cycle again
  • Enter the G0 phase
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71
Q

“Acidophilic tissues take acidic stains → Eosin” - True/False

A

TRUE

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72
Q

What colour does Eosin stain?

A

Pink

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73
Q

“Basophilic tissues take basic stains → Hematoxylin” - True/False

A

TRUE

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74
Q

What colour does Hematoxylin stain?

A

Purple

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75
Q

What are the 4 basic tissue types?

A
  • Epithelium
  • Connective tissue
  • Muscle tissue
  • Nervous tissue
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76
Q

What is the primary function of epithelial tissue?

A
  • covers body surfaces
  • lines hollow organs
  • forms glands
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77
Q

How are epithelial cells connected to each other?

A

Through their cytoskeleton

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78
Q

What is the role of the basal lamina (basement membrane) in epithelial tissue?

A
  • thin layer of specialised extracellular material that separates the basal surface of epithelial cells from underlying tissue and provides support
  • non-vascular: lacks blood vessels
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79
Q

How are epithelial cells polarised, and what do the apical and basal sides refer to?

A
  • Apical side: facing lumen or external environ
  • Basal side: attaching to basement membrane.
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80
Q

List some functions of epithelial tissue

A
  • Mechanical barrier (e.g., skin) -
  • Chemical barrier (e.g., lining of the stomach),
  • Facilitates diffusion,
  • Absorption/secretion,
    Containment (e.g., urinary bladder lining)
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81
Q

How would you classify a cell?

A
  1. No. layers of cell
  2. Cell Shape
  3. Cell/Tissue Surface
  4. Presence of any specialised cell types
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82
Q

How many layers of cells are present in SIMPLE epithelium?

A

1

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83
Q

How many layers of cells are present in STRATIFIED epithelium?

A

2 or more

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84
Q

How many layers of cells are present in PSEUDOSTRATIFIED epithelium?

A

Multiple layers but all cells make contact with basal lamina

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85
Q

How would you describe the shape of SQUAMOUS epithelial cells?

A

Flattened

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86
Q

How would you describe the shape of CUBOIDAL epithelial cells?

A

Cube

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87
Q

How would you describe the shape of COLUMNAR epithelial cells?

A

Tall and thin

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88
Q

What are microvilli, and what is their function?

A

Finger-like projections at apical end of cells that increase SA and aid in absorption
- found in digestive system

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89
Q

Name the surface specialisation involved in moving substances across the cell surface

A

Cillia

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90
Q

What does it mean for a tissue to be “keratinised”?

A

These tissues contain a tough, protective protein called ‘keratin’, often found in the skin, hair, and nails

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91
Q

What is an example of specialised cells with nuclei located at the bottom, associated with mucus secretion?

A

Goblet Cells

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92
Q

How do endocrine glands release their products, and what happens to these products?

A

Lack ducts and release their products, eg: hormones, directly into bloodstream - distributed throughout body via vascular system.

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93
Q

What distinguishes exocrine glands from endocrine glands in terms of product release?

A

Exocrine glands secrete their products onto a surface directly through a duct

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94
Q

What are the two main types of soft connective tissue and where are they located?

A

Loose and dense CT
- tissues and tendons

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95
Q

How are collagen fibres arranged in dense REGULAR connective tissue, and give an example?

A

Aligned in parallel fashion
- eg: tendons

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96
Q

Describe the arrangement of collagen fibres in dense IRREGULAR connective tissue and give an example?

A

Run in many directions
- eg: ligaments.

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97
Q

How does dense connective tissue differ from loose connective tissue?

A

Dense: densely packed bundles of collagen fibres
Loose: loosely packed fibres separated by ground substance

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98
Q

What are the characteristics of cartilage?

A
  • Type of hard CT
  • strong, flexible, compressible, and semi-rigid tissue that is avascular (lacks blood vessels)
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99
Q

What are the 3 types of cartilage?

A
  • Hyaline, Elastic, and Fibrocartilage
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100
Q

What makes hyaline cartilage different?

A

Glassy appearance
- most common type, found in every joint

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101
Q

What makes elastic cartilage different?

A

Contains thin elastic fibres that provide elasticity

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102
Q

What makes fibrocartilage different?

A

Contains more collagen, making it tougher and gives additional strength to other parts
- eg: intervertebral discs.

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103
Q

What are the 2 main types of bone tissue and their difference?

A
  • Cortical: dense outer shell with no cavities
  • Spongy/Trabecular bone: with numerous interconnecting cavities
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104
Q

What are Osteons?

A

Characteristic structures of mature bone formed during bone remodeling

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105
Q

What are the key cell types associated with Osteons?

A
  • Osteocytes (bone cells)
  • Osteoclasts (bone-resorbing cells)
  • Osteoblasts (bone-forming cells)
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106
Q

What are the 2 main components of the extracellular matrix (ECM)?

A
  • Organic matrix (collagen and glycoproteins)
  • Inorganic matrix (calcium and minerals)
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107
Q

What is the primary role of chondrocytes in CT?

A
  • Metabolically active cells
    responsible for synthesising and turning over a large volume of ECM
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108
Q

How are blood and lymph classified in terms of CTs?

A

Fluid CTs

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109
Q

What is the primary function of muscle tissue, and how does it achieve this function?

A
  • specialised to generate force by contraction
  • achieved through movement of actin fibres over myosin fibres.
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110
Q

What are the 3 types of muscle tissue?

A
  • Smooth
  • Cardiac
  • Skeletal
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111
Q

What are the properties of Smooth muscle?

A
  • Involuntary, non-striated
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112
Q

What are the properties of Cardiac muscle?

A
  • Involuntary, striated, single nucleus at centre of fibre, intercalated discs: contains intracellular junctions for stability
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113
Q

What are the properties of Skeletal muscle?

A

Voluntary, striated, multinucleated with peripheral nuclei (no nucleus at centre)

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114
Q

What does Nervous tissue consist of?

A

Neurons and their supporting gila cells

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115
Q

Give examples of structures where nervous tissue is found in the CNS and PNS

A
  • CNS: the meninges
  • PNS: the perineurium
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116
Q

What is the primary function of nervous tissue?

A

Allows for rapid communication between different parts of the body, facilitating the transmission of electrical signals/info

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117
Q

What characterises a Multipolar neuron?

A
  • most common type
  • multiple dendrites, one axon.
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118
Q

What characterises a Bipolar neuron?

A

one dendrite, one axon.

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119
Q

What characterises a Pseudounipolar neuron?

A

Single process that divides into a peripheral and central branch

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120
Q

What is the function of Microglia in CNS?

A

Responsible for immune surveillance

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121
Q

What is the function of Astrocytes in CNS?

A

Provide support and are involved in ion transport

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122
Q

What is the function of Oligodendrocytes in CNS?

A

Produce myelin which insulates and speeds up nerve cell conduction

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123
Q

What is the primary function of Schwann cells in PNS?

A

Produce myelin and provide support to axons.

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124
Q

What is the sequence of blood vessels from arteries to veins?

A

arteries → arterioles → capillaries → venules → veins

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125
Q

Name the three main types of blood vessels

A

arteries, veins, and capillaries

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126
Q

Describe the structure of the Tunica Intima (inner layer)

A

Consists of single layer of squamous epithelial cells (endothelium) supported by a basal lamina and a thin layer of CT
- separated from the t.media by internal elastic membrane

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127
Q

Describe the structure of the Tunica Media (middle layer)

A
  • Composed of smooth muscle cells
  • separated from the t.adventitia by external elastic membrane
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128
Q

Describe the structure of the Tunica Adventitia (outer layer)

A
  • Composed of supporting CT
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129
Q

What characterises the structure of the largest arteries, such as the aorta?

A
  • Elastic arteries contain multiple sheets of elastic fibres in their t.media, providing elastic recoil to handle high-pressure blood.
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130
Q

What is the function of Vasa Vasorum?

A

Responsible for delivering nutrients and oxygen to the walls of arteries/ veins while removing waste products

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131
Q

What is the structure of arterioles?

A
  • only 1/2 layers of smooth muscle in their t.media
  • minimal adventitia
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131
Q

How does the amount of smooth muscle change as arteries become smaller?

A

Smaller

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132
Q

What are the main components of capillaries?

A

Consist of endothelial cells and basal lamina

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133
Q

What types of capillaries are there?

A
  • Continuous: (no pores, found in muscle, nerve, skin)
  • Fenestrated (small pores, found in kidney)
  • Discontinuous (large gaps, found in liver)
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134
Q

In which tissues/structures are capillaries absent?

A

-In epithelial cells resting on the basement membrane
- Epidermis of skin, hair, nails
- Cornea of eye
- Hyaline cartilage

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135
Q

What are the components of the Microvasculature, and what role does each play?

A
  • Meta arterioles (branches of small arterioles, pre-capillary)
  • Pre-capillary sphincters (control flow to the meta arterioles and capillaries), - Thoroughfare channels (allow flow when pre-capillary sphincters are closed, saving material and heat)
  • Capillaries (material exchange occurs).
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136
Q

What is the sequence of blood vessels from large vein to venule?

A

large vein → medium vein → small vein → venule

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137
Q

Describe the structure of postcapillary venules

A

Consist of endothelium and a thin layer of CT

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138
Q

How do venules differ from postcapillary venules in terms of smooth muscle presence?

A
  • Venules: intermittent smooth muscle in t.media
  • Postcapillary venules: no significant smooth muscle layer
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139
Q

What are the key structural components of veins?

A

T.intima, a thin continuous t.media, t. adventitia

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140
Q

What is the unique feature of the vena cava, the largest vein in the body?

A

Has a thick t.adventitia that incorporates bundles of oriented smooth muscle

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141
Q

What is the primary function of the lymphatic vascular system?

A

Transports lymph to lymph nodes for immunological surveillance

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142
Q

How does the lymphatic vascular system move waste into the bloodstream, and what mechanisms are involved?

A
  • Tissue pressure
  • Muscle contraction
  • Presence of valves in the lymphatic vessels
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143
Q

What is the average blood volume?

A

6L - separated by spinning in a centrifuge

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144
Q

In a centrifuged blood sample, what is the order of components from bottom to top?

A
  • Top: Plasma
  • Middle: WBCs
  • Bottom: Erythrocytes (RBCs)
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145
Q

How is serum formed in the blood?

A

When blood clots are removed after the clotting factors have been taken out

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146
Q

What is the difference between serum and plasma?

A

Plasma contains clotting factors, while Serum does not.

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147
Q

What is the primary component of plasma, and what is its function?

A
  • Water (about 90%) - plasma is worth 55%
  • it carries various proteins (albumin, immunoglobulins, clotting factors)
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148
Q

Explain the roles of hydrostatic pressure and osmotic pressure in plasma dynamics

A
  • Hydrostatic pressure: forces plasma components into cells
  • Osmotic pressure: draws water out of capillaries due to low water concentration on the venous side
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149
Q

What are the main components of formed elements in blood, and what are their characteristics?

A

45% - Erythrocytes (red blood cells) that are biconcave discs with no nucleus
- stain red (haemogloblin)

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150
Q

What is the primary role of platelets in the blood?

A
  • role in hemostasis (prevention of blood loss)
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151
Q

What are Granulocytes, and which 3 types are found in blood?

A
  • white blood cells with granules in their cytoplasm

neutrophils, eosinophils, and basophil

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152
Q

What are the characteristics and functions of Neutrophils?

A

Single, multi-lobed nucleus
-make up 40-75% of WBCs
-Function as phagocytes when activated

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153
Q

What are the characteristics and functions of Eosinophils?

A
  • have acidic granules that stain pink, bi-lobed nucleus, and make up 5% of WBCs.
  • Granules contain hydrolytic enzymes involved in inflammation.
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154
Q

What are the characteristics and functions of Basophils?

A
  • Bi-lobed or S-shaped nucleus, basic granules that stain purple/blue (different from eosinophils), and make up 5% of WBCs.
  • Serve as effector cells in allergic reactions
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155
Q

What are Agranulocytes, and which 2 types are found in blood?

A
  • WBCs without granules in their cytoplasm
    Monocytes and Lymphocytes
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156
Q

Describe the characteristics and functions of Monocytes

A
  • Large kidney bean-shaped nucleus, make up 1-5% of WBCs
  • Serve as precursors of tissue macrophages, functioning as phagocytes.
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157
Q

Describe the characteristics and functions of Lymphocytes

A
  • Small spherical nucleus and basophilic (blue) cytoplasm. Make up 20-50% of WBCs and can differentiate into B cells, which give rise to antibody-secreting plasma cells, and T cells, which have various defensive functions
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158
Q

What is Hemopoiesis?

A

= development of blood cells
- earliest blood cell development occurs about 3 weeks into gestation

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159
Q

Where does the majority of blood cell development occur, and what is responsible for producing blood cells?

A
  • Development occurs in the second trimester within bone marrow
  • B.M responsible for producing blood cells
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160
Q

What is the charge and mass of Protons?

A

+ charge
Mass of + 1

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161
Q

What is the charge and mass of Electrons?

A
  • charge
    Mass: negligible (too small)
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162
Q

What is the charge and mass of Neutrons?

A

No charge
Mass of 1

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163
Q

What type of bond is formed when unpaired electrons are shared, and it’s the strongest type of bond?

A

Covalent bonds

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164
Q

What is the attraction of opposite charges called?

A

Ionic bond

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165
Q

What type of bond involves the sharing of hydrogen atoms?

A

Hydrogen bond

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166
Q

What is the term for the interaction of non-polar substances in the presence of polar substances, especially water?

A

Hydrophobic interaction

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167
Q

What is van der Waals interaction?

A

Interaction of electrons of non-polar substances

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168
Q

What does Electronegativity refer to?

A

The attractive force that an atomic nucleus exerts on electrons within a bond

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169
Q

What is the addition/removal of a Phosphoryl group called?

A

(De)Phosphorylation

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170
Q

What is the process of adding an Acyl group to a molecule called, and why is it useful?

A

Acylation:
- stable and useful for joining molecules

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171
Q

What does Carboxylation involve, and where does it usually occur on a molecule?

A

Involves the addition of a carboxyl group
- occurs at end of a molecule, often at its reactive centre.

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172
Q

In which type of reaction does the addition of an acid and alcohol group produce an ester bond, and what is released during this process?

A

Esterification
- water is released

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173
Q

What happens in a Condensation reaction, and what is the result?

A

Water is removed
- molecules polymerise, forming larger compounds

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174
Q

What occurs in a Hydrolysis reaction, and what’s the effect on molecules?

A

Water is added
- molecules depolymerise/break down into smaller components

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175
Q

What are Oxidation-Reduction (redox) reactions?

A

Involve transfer of electrons from one molecule to another
- O: loss
- R: gain
Redox pairs: one molecule is oxidised while another reduced

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176
Q

What factors can cause the oxidation state of carbon to vary in a molecule?

A

Molecule’s structure and electronegativity differences

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177
Q

“Charge imbalances help form reactive groups on biological molecules” - True/False

A

TRUE

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178
Q

What are Monosaccharides?

A

Carbs with SINGLE ring structure

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179
Q

What are Disaccharides?

A

Carbs with DOUBLE ring structure

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180
Q

What are Polysaccharides and their function?

A

Long chains of monosaccharides
- serve as storage carbs
- eg: Glycogen- rapid metabolism of glucose.

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181
Q

What is the 1st law of Thermodynamics?

A

Energy is neither created nor destroyed (conserved)

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182
Q

What do thermodynamic reactions involve a change in, and why is this important?

A

-Enthalpy: heat content
- Entropy: randomness/disorder
- affects free energy of system + determines whether a reaction is spontaneous or requires energy

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182
Q

What is the 2nd law of Thermodynamics?

A

Energy transformations aren’t 100% efficient
- some energy loss in form of heat

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183
Q

How is the change in free energy (ΔG) calculated?

A

𝝙G = Energy of Products (𝝙H) – Energy of Reactants (T 𝝙S)

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184
Q

What does a ΔG value near 0 indicate about a chemical reaction?

A

Reaction is in state of equilibrium readily reversible (proceed in forward or reverse direction)

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185
Q

What characterises EXERGONIC reactions?

A
  • Negative ΔG
  • Energy of products < Energy of reactants
  • occur spontaneously + release energy used for cellular processes
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186
Q

What characterises ENDERGONIC reactions?

A
  • Positive ΔG
  • Energy of products > Energy of reactants
  • cannot occur spontaneously + require energy input to proceed
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187
Q

What is Metabolism?

A

All biochemical reactions occurring within body

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188
Q

What is Catabolism?

A

Breaking down complex molecules into simpler ones, releasing energy (exer.and oxidative)

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189
Q

What is Anabolism?

A

Synthesis of complex molecules from simpler ones + requires energy input (ender. and reductive).

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190
Q

Why is water polar?

A

Electrons are shared unequally, enabling it to act as a universal solvent.

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191
Q

How does the hydrophobic effect influence the behaviour of non-polar substances in aqueous solutions?

A

Non-polar substances aggregate in aq.solutions and exclude water molecules, leading to formation of structures like micelles, lipid bilayers, ‘oil slicks.’

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192
Q

What is the primary function of cell membranes?

A

Act as selective and controllable barriers to outside world

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193
Q

What are Amphipathic molecules, and their role in cell membranes?

A
  • Polar hydrophilic head and Non-polar hydrophobic tail
  • form micelles and lipid bilayer of CMs
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194
Q

What is the basic structure of amino acids?

A

⍺-carbon bonded to:
- Amino group (-NH2)
- Carboxyl group (-COOH)
- A hydrogen (-H)
- A side chain (-R)

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195
Q

What does “polar” mean?

A

Uneven distribution of electrons: partial positive and negative charges, making them hydrophilic (water-attracting)

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196
Q

What are the classifications of amino acids?

A
  • Non-polar, Hydrophobic
  • Polar, Hydrophilic
  • Acidic
  • Basic
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197
Q

What does “non-polar” mean?

A

Even distribution of electrons: no significant partial charges, making them hydrophobic (water-repelling)

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198
Q

How are peptide bonds formed?

A

Formed by endergonic process, joining amino acids through condensation reaction

  • strong, rigid, crucial for protein folding
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199
Q

Do peptides have a specific direction?

A

Yes:
- N-terminus (left/amino end)
- C-terminus (right/carboxyl end).

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200
Q

What is the nature of the peptide bond?

A

-partial double bond
- planar in structure

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201
Q

What are Bases?

A

Proton acceptors

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202
Q

What defines an Acid?

A
  • Proton (H+) donor
  • Strength depends on how readily it donates a proton to base, which is measured by acid dissociation constant (Ka)
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203
Q

What is pH?

A

Measurement of number of protons (H+) in solution
- Formula: pH = -log10[H+].

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204
Q

What is the Henderson-Hasselbalch equation used for?

A

Connects Ka (acid dissociation constant) of weak acid with pH of solution containing this acid
- expressed as: pH = pKa + log[A]/[HA]

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205
Q

What are Buffers and their significance?

A

Solutions used to control pH of reaction mixture
- At pKa value, buffers resist change in pH when moderate amounts of acid/base added, as long as the conc of acid is equal to the conc of conjugate base.

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206
Q

“Proteins can act as buffers” - True/False?

A

TRUE
- Haemoglobin in blood

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207
Q

What are Zwitterions?

A

Molecules with no charged side groups but have separate positively/negatively charged ions

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208
Q

How can changes in pH affect proteins?

A

Change in ionisation leading to changes in structure/ function

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208
Q

What are the angles around which polypeptides can rotate?

A

Between Alpha carbon and amino group

Alpha carbon and carboxyl group

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209
Q

What does the primary level of protein structure refer to?

A

Sequence of amino acid residues in polypeptide chain

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210
Q

What is the secondary structure of proteins characterised by?

A

Localised conformations of the polypeptide backbone that are held together by hydrogen bonds

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210
Q

Name the 3 types of secondary protein structure

A
  • Alpha helix
  • Beta sheets (strands and sheets)
  • Triple helix
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211
Q

What characterises the ALPHA helix in protein secondary structure?

A

Polypeptide chain where the CO group of one amino acid forms hydrogen bonds with the NH group of another amino acid located 4 residues away

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212
Q

Describe the features of BETA SHEETS in protein secondary structure

A
  • (anti)/parallel and turns between strands
  • form zigzag beta-pleated sheets.
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213
Q

What is the TRIPLE HELIX in protein secondary structure, and where is it commonly found?

A

Component of proteins in bone and tissue
- most abundant in vertebrates and forms water-insoluble fibres
- eg: Tropocollagen

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214
Q

What is the role of Collagen in the body?

A

Influences strength of CT

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215
Q

What happens to collagen with age, and how does it affect tissues?

A

Undergoes covalent crosslinking as age increases
- weaken tissues

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216
Q

What is a clinical sign of weakened collagen?

A

Bleeding gums, Skin discolouration (Scurvy)

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217
Q

What is the Tertiary structure of a protein?

A

3D arrangement of entire polypeptide chain

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218
Q

What forces stabilises the Tertiary structure of a protein?

A
  • Covalent disulfide bonds
  • Electrostatic interactions (salt bridges)
  • Hydrophobic interactions
  • Hydrogen bonds (in backbone and side chains)
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219
Q

Give examples of Fibrous proteins and their characteristics

A

Keratin found in hair and wool: mechanically strong structures with parallel polypeptide chains aligned along a single axis
- insoluble in water

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220
Q

Provide an example of a Globular protein and its characteristics.

A

Haemoglobin:
- spherical shape
- soluble in water/salt solutions

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221
Q

What is Quaternary structure in proteins?

A

Spatial arrangement of polypeptide chains in a protein with multiple subunits.

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222
Q

Provide an example of a protein with Quaternary structure and its characteristics (1)

A

Hemoglobin
- 4 subunits : 2 ⍺ and 2 β chains. Each subunit contains 1 haem group, binds to oxygen - changes affinity of other subunits for oxygen.

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223
Q

Provide an example of a protein with Quaternary structure and its characteristics (2)

A

Tropocollagen
- structural unit of a collagen fiber
- formed by 3 helical chains twisted around each other to create a right-handed superhelix
- contains interchain hydrogen bonds and intermolecular covalent bonds.

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224
Q

How do proteins typically fold into their correct shape, and what can go wrong in this process?

A

Fold spontaneously but can be slow and proteins may fold incorrectly before completely synthesised or associate with other proteins before folding properly: lead to conditions like Alzheimer’s, Parkinson’s, OCD

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225
Q

Factors that can disrupt the structure of proteins?

A
  • Heat: increases vibrations in proteins
  • pH extremes: disrupt electrostatic interactions
  • Detergents and urea: disrupt hydrophobic interactions
  • Thiol agents and reducing agents: disrupt disulfide bonds
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226
Q

What is Homeostasis?

A

Maintenance of steady states within our bodies coordinated by physiological mechanisms.

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227
Q

What are the 2 types of homeostatic control systems?

A
  • Intrinsic: controls inside organ
  • Extrinsic: mechanisms initiated outside an organ, accomplished by nervous and endocrine systems
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228
Q

What is the difference between Feedforward and Feedback systems?

A
  • Feedforward: responses made in anticipation of change
  • Feedback: after change detected
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229
Q

Describe the components of a feedback system

A

Sensor, Control center, Effector
- promote stability

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230
Q

What is the purpose of a Negative feedback system?

A

Oppose initial change in controlled variable, maintain stability and keep physiological conditions within narrow range

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231
Q

How do Positive feedback systems function?

A

Amplify an initial change in a controlled variable
- leading to rapid and dramatic physiological responses

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232
Q

Provide examples of variables regulated by negative feedback mechanisms?

A
  • Mean Arterial Blood Pressure
  • Core Body Temperature
  • Blood Glucose
  • Blood Gases (arterial PO2 and PCO2)
  • Blood H+ concentration (pH)
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233
Q

What are the steps involved in maintaining homeostasis through negative feedback control?

A

Sensor → Control centre → Effector

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234
Q

How do X-rays produce an image?

A
  • Electric current heats cathode
  • Electrons emitted + strike the anode
  • X-rays exit through a window, penetrate patient, and scatter
  • Denser tissues allow fewer X-rays to pass through, forming the image
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235
Q

What are the strengths of X-rays?

A
  • Reveals structures surrounded by bone
  • Highlights abnormalities that damage white bone, eg: cancer
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236
Q

What are the weaknesses of X-rays?

A
  • Radiation (health risks)
  • Abnormality must be different density to surrounding tissue in order to be visible
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237
Q

What is a Gamete?

A

Mature haploid male/female germ cell which is able to unite with another of the opposite sex in sexual reproduction to form a zygote

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237
Q

What is Teratogen?

A

Factor that can cause abnormalities in a developing fetus

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238
Q

What is a Mutagen?

A

Cause mutations in genetic material

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239
Q

What happens during Week 0-3?

A

Conceptus/Embryo

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240
Q

What happens during Week 3-8?

A

EMBRYONIC PERIOD

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240
Q

What happens during Week 9-40?

A

Foetal period

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241
Q

The Phases of Embryogenesis are…?

A
  • Gametogenesis
  • Fertilisation
  • Cleavage
  • Gastrulation
  • Formation of Body Plan
  • Organogenesis
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242
Q

What happens during Gametogenesis?

A
  • Formation of gametes:
    Spermatogenesis: formation of male gametes
    Oogenesis: formation of female gametes - Primary oocytes begin meiosis by weeks 28-30 but arrest in prophase until puberty
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243
Q

What is the significance of the Zona Pellucida in oocyte development?

A
  • Tough protective protein coat around oocyte
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244
Q

What happens during Fertilisation (Week 1)?

A

Fusion of sperm and oocyte to form zygote
- in ampulla of uterine tube

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245
Q

What happens during Cleavage (Week 1)?

A

Rapid mitotic cell division process, with no increase in size, resulting in small cells (Blastomeres)

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246
Q

What are the stages of early embryonic development from zygote to blastocyst?

A

Zygote → Morula → Blastocyst

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246
Q

What happens during Gastrulation (Weeks 2-3)?

A

Formation of germ layers (body axis):
- Ectoderm (outer) - skin, nervous tissue
- Mesoderm (middle) - muscle tissue, organs
- Endoderm (inner) - GI lining tract

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247
Q

What is the process of “Formation of body plan” ?

A

Folding of embryo, leading to creation of 3D human shape

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248
Q

What is meant by “tube within tube” during embryonic folding?

A

Structural arrangement where GI tube develops within embryo, forming the basis for digestive system

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248
Q

What happens during Organogenesis (Week 3-8)?

A

Formation of organs

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249
Q

What happens during Feotal Period (Week 9+)?

A
  • Significant growth and weight gain, – Maturation of tissues and bone development
  • Establishment of connections in CNS
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250
Q

Primary processes of Embryonic development?

A
  • Cell division: increase no. cells
  • Differentiation: specialisation
  • Cell attachment: formation of tissues
  • Apoptosis: programmed cell death
  • Induction: ability of one cell to cause another to differentiate
  • Cell migration: movement from one location to another
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250
Q

Secondary processes of embryonic development?

A
  • Axis formation/Polarity
  • Folding/Rotation
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251
Q

Factors responsible for the regulation of embryonic development?

A

Genetic, Epigenetic (environ.)

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252
Q

What is Trisomy 21?

A

Downsyndrome:
- caused by nondisjunction (failure of chromosomes to separate)

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253
Q

What is the 2nd step in Fertilisation?

A

Acrosomal enzymes are released from sperm head - sperm digests its way into egg

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253
Q

What is the 1st step in Fertilisation?

A

Sperm binds to Zona Pellucida glycoprotein (ZP3)

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254
Q

What is the 3rd step in Fertilisation?

A

Egg and sperm plasma membranes fuse - sperm content enters egg

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254
Q

What is the 4th and final step in Fertilisation?

A

Sperm entry triggers completion of Meiosis 2 in egg and the release of cortical granules by the oocyte
- makes zona pellucida impenetrable to other sperm

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255
Q

8 cell stage blastomeres are…?

A

Totipotent
- potential to develop into any cell type

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256
Q

What is Mosaicism?

A

2/more genetically different sets of cells in body
- due to mitotic dysfunction

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257
Q

What is Compaction, and when does it occur during embryonic development?

A
  • Where cells are confined within ZP causing embryo to change shape
  • occurs during transition from morula to blastocyst
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258
Q

What role does fluid play in the formation of a blastocyst?

A

Fluid enters through ZP, contributing to transformation of Mor. into Blas. and facilitating the formation of gap junctions among outer cells

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259
Q

Describe the stages involved in the formation of a Blastocyst

A

Morula (zygote divided into 16+ cells) and then Blastocyst (200-300 cells)
- Cells maximise space, closer contact with each other, form cell junctions

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260
Q

What is Blastocyst hatching?

A

Blastocyst expands until it bursts through ZP

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260
Q

What is the role of Progesterone in fertility?

A

Aids fertility by maintaining thickness of endometrial wall

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261
Q

What are the key components of the Blastocyst and their functions?

A
  • Outer cell mass (Trophoblast): allows embryo to interact directly with endometrial lining of uterus for implantation and forms placenta
  • Inner cell mass (Embryoblast): responsible for formation of embryo
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262
Q

When does Implantation occur during pregnancy?

A

By Day 6 - after fertilisation

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263
Q

What is Implantation?

A

When the fertilised egg attaches and embeds itself into the lining of the uterus

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264
Q

What is an Ectopic pregnancy, and how does it differ from a normal implantation?

A

When implantation occurs outside uterus

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265
Q

What is Placenta Previa?

A

Placenta lies low in uterus and partially/completely covers cervix

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266
Q

What happens on Day 7.5 of embryonic development?

A
  • Trophoblast divides into cytotrophoblast (individual cells) and syncytioblast (single multinucleated cell which produces hCG)
  • Embryo organises into epiblast (dorsal surface) and hypoblast (ventral surface)
  • Amniotic cavity begins to form
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267
Q

What happens on Day 9 of embryonic development?

A
  • Formation of 2 cavities:
    • amniotic cavity (epiblast)
    • primitive yolk sac (hypoblast)
  • Implantation complete, closure by fibrin coagulum
  • Vacuoles in syncytiotophoblastand unite to form lacunae
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268
Q

What happens on Day 12 of embryonic development?

A

-Uteroplacental circulation established
- maternal blood flows into lucunae to diffuse to embryoblast
- Extraembryonic mesoderm (outside) develops then degenerates,
- forming chorionic cavity

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269
Q

What happens on Day 13 of embryonic development?

A
  • Further development of chorionic cavity
  • Presence of connecting stalk (later umbilical cord)
  • Second wave of hypoblast cells migrate to form definitive yolk sac
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270
Q

What happens during Week 3?

A

Primitive Streak - appears in midline at caudal end of epiblast
- Cranial end of PS = Primitive Pit and Node

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271
Q

What is Pulse, and what’s the normal resting heart rate for adults?

A

Measures heart rate
- 60-100 beats per minute

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272
Q

What is considered Normal Blood Pressure?

A

Around 120/80 mmHg, with a range of 70-105 mmHg

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273
Q

What is the normal Respiratory Rate in adults?

A

12-20 breaths per minute

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274
Q

What is the normal Oxygen Saturation level?

A

Equal to or greater than 96%

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275
Q

What is the normal Body Temperature?

A

37.8 degrees Celsius

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275
Q

How is Consciousness assessed using AVPU?

A

“A” representing conscious

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276
Q

What is the normal Capillary Refill time?

A

Less than 2 seconds

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277
Q

What are the effects of body temperature on cellular metabolism?

A
  • Increased temp = faster metabolism
  • Decreased temp = slower metabolism
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278
Q

What factors can cause variations in core body temperature?

A

Menstrual cycle, activity, exercise, emotions

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279
Q

What is Normothermia, and why is it important?

A

Maintaining normal body temp within narrow range despite environ changes
- essential for optimum cellular metabolism and function

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279
Q

What are the consequences of Overheating on the body?

A

Protein denaturation, Nerve malfunction, Death

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280
Q

What is the purpose of monitoring body temperature at peripheral sites?

A

Used for indirect estimate of core body temp

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280
Q

Examples of devices used for indirect estimation of core body temp?

A

Infrared tympanic thermometers,
Infrared forehead thermometers, Forehead strips

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281
Q

Why should peripheral sites like oral, sublingual, or axillary measurements be avoided for estimating core body temp?

A

Less accurate estimates of body temp

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282
Q

Which body site is commonly used in clinical practice for temp monitoring?

A

Ear drum (tympanic)

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283
Q

What is the normal temp range for the ear drum (tympanic)?

A

Between 36°C and 37°C

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284
Q

At what temp range is a person considered to have a fever?

A

38°C or higher

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285
Q

What temp range indicates Hyperthermia?

A

40°C or higher

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286
Q

What temp range indicates Hypothermia?

A

Below 35°C

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287
Q

What is Metabolic Heat, and what contributes to it?

A

Includes Basal Metabolic Rate (BMR), the basic level of heat production, which can increase due to hormones like adrenaline and noradrenaline

  • Muscle activity, such as shivering, generates heat
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288
Q

What are the 3 main mechanisms of heat loss?

A
  • Radiation (emission of heat energy as electromagnetic waves)
  • Conduction (transfer of heat between objects in contact, moving from warmer to cooler objects)
  • Convection (movement of air carrying heat)
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289
Q

How much does Radiation contribute to heat loss?

A

Accounts for half of body’s heat loss

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290
Q

What factors influences Conduction?

A

Temp gradients and Thermal conductivity
- combines with Convection

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291
Q

Explain the process of Convection

A

When air next to the skin is warmed by conduction, causing warmed air to rise due to its lower density while cooler air moves in next to the skin

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291
Q

What are the 2 types of Evaporation in heat regulation?

A
  • Passive: where water passively diffuses from the skin and respiratory linings
  • Active: involves sweating controlled by the sympathetic nervous system (SNS).
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292
Q

What is the first step in temperature regulation? Name 2 types of thermoreceptors involved?

A
  • Sensor detection
    Central and Peripheral thermoreceptors
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293
Q

What are the effectors in temperature regulation, and what is their role?

A
  • Skeletal muscles, Skin arterioles, Sweat glands
    trigger responses to restore the temp variable to normal
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293
Q

Example of response to WARMTH

A

Sweat Glands: SWEATING
- Skin arterioles: VASODILATE
- Skeletal muscles: DECREASED MUSCLE TONE

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293
Q

What does the sensor do when it detects a temperature change?

A

Sends signal to hypothalamus

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293
Q

How does the Hypothalamus respond to temperature changes?

A

2 centres:
- Posterior center activated by COLD
- Anterior center activated by WARMTH

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293
Q

Example of response to COLD

A
  • Skin arterioles: VASOCONSTRICT
  • Skeletal muscles: SHIVERING, INCREASED MUSCLE TONE
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294
Q

What is the initial step in the development of fever?

A

Macrophages release endogenous pyrogen

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295
Q

What does endogenous pyrogen stimulate in response to fever?

A

Hypothalamus to release prostaglandins

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296
Q

When does the thermostat reset to normal in a fever?

A

If the release of pyrogen is reduced or stopped

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297
Q

How does the body respond to increase temperature during fever?

A

Hypothalamus initiates mechanisms to heat the body, including shivering and vasoconstriction

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298
Q

What happens to the body’s thermostat during fever?

A

Prostaglandins “reset” the thermostat to a higher temp

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298
Q

What type of information is held in the sequence of DNA bases?

A

Genetic information

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299
Q

What is the composition of the DNA backbone, and what are the base pairings?

A
  • consists of sugar-phosphate backbone (deoxyribose)
  • base pairings are adenine (A) with thymine (T) and cytosine (C) with guanine (G)
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300
Q

In what direction is DNA read and replicated, and how is the DNA structure oriented?

A

5’→3’ direction
- Antiparallel structure

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301
Q

How is DNA organised within the cell nucleus?

A

DNA strands are associated with Histones and wound into chromosomes within the cell nucleus

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302
Q

“DNA replication is error-prone and susceptible to damage, leading to mismatched bases, strand breaks, and chemical cross-linking.” TRUE/FALSE

A

TRUE

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302
Q

What are the phases of the cell cycle, and when does DNA synthesis occur?

A

G1, S, G2, and M phases
- DNA synthesis occurs during S phase

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303
Q

What is the outcome of Mitosis, and how does it relate to mutations?

A
  • 1 diploid parent cell giving rise to 2 identical diploid daughter cells.
    Mutations acquired are somatic (not inherited) - every cell can acquire them
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304
Q

What is the outcome of Meiosis, and what is a key feature during this process?

A
  • 1 diploid parent cell produces 4 haploid daughter cells
  • Key feature: crossing over (P1), where genes segregate independently, even if they are on same chromosome. Meiosis crucial for gamete formation.
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304
Q

What is the central dogma of molecular biology, and what factors can affect it?

A
  • Flow of genetic information from DNA to RNA to protein
  • affected by: transcription rate, splicing and polypeptide processing, and mRNA half-life
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304
Q

What are the key characteristics of RNA?

A
  • Single-stranded
  • Ribose sugar backbone
  • uses Uracil (U) instead of Thmine (T) in its base pairs.
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305
Q

What is a Variant in the context of the human genome?

A

Change in DNA sequence

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306
Q

Define Mutation

A

Any heritable change in DNA sequence

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307
Q

What are the 2 types of sequence variations that can occur within a gene?

A

Changes in the:
- Promoter sequence (initiates gene expression)
- Exon sequence (contains coding info for protein synthesis)

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308
Q

What is a Polymorphism and its population frequency?

A

Variant that doesn’t cause disease on its own
- PF greater than 1%

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308
Q

What are Single Nucleotide Polymorphisms (SNPs), and how can they affect gene function?

A

Genetic variations that involve single nucleotide changes.
- prone to disease, often by altering transcription, such as modifying promoter region

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309
Q

What are Copy Number Variations (CNVs)?

A

Variations that involve extra/missing stretches of DNA, such as deletions/duplications

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309
Q

What does a Nucleoside consist of?

A

Base and 5-carbon sugar

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310
Q

What does a Nucleotide consist of?

A

Nucleoside and Phosphate group

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311
Q

Name the purine bases found in DNA and RNA

A

Adenine and Guanine

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312
Q

Name the pyrimidine bases found in DNA, and which one is replaced in RNA?

A

DNA: A,C,G, T
RNA: A,C,G, U

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313
Q

What type of bonds form between nucleotides in DNA?

A

Phosphodiester bonds form between the 3’ hydroxyl group and the 5’ triphosphate, linking nucleotides together

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314
Q

Describe the structure of DNA

A
  • Anti-parallel double helix structure, with one strand running from 5’ to 3’ and other from 3’ to 5’
  • Sugar-phosphate backbone and base pairs on inside, held together by hydrogen bonds
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315
Q

What is the initial requirement for DNA replication?

A

DNA Primer

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316
Q

What enzyme unwinds the DNA helix during replication?

A

DNA Helicase

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317
Q

What is the structure formed during DNA replication, and what are its components?

A

Replication Fork
- consists of leading and lagging strands

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318
Q

In which direction is the leading strand synthesised during DNA replication, and which enzyme catalysses this process?

A

5’→3’ direction
- DNA polymerase catalyses this synthesis

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319
Q

How is the lagging strand synthesised during DNA replication, and how are its fragments joined?

A

Synthesized in Okazaki fragments - joined together by DNA ligase

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320
Q

In eukaryotes, how does replication begin, and what is the advantage of this process?

A

Starts simultaneously at several points in genome
- speeds up replication process and is bidirectional.

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321
Q

What is the role of rRNA in the cell?

A

Combines with proteins to form ribosomes (protein synthesis)

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322
Q

What is the function of tRNA in protein synthesis?

A

Carries amino acids to be incorporated into proteins during Translation

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323
Q

What is the main role of mRNA in the cell?

A

Carries genetic information from DNA to ribosomes for p.synthesis

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324
Q

What are RNA polymerases, and how many types are found in eukaryotes?

A

Multi-subunit complexes responsible for making RNA
- Pol I, Pol II, Pol III

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325
Q

Which RNA polymerase synthesises all mRNA?

A

Pol II

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326
Q

What is the function of TATA box in transcription, and how does it relate to the TATA box Binding Protein (TBP)

A

At (-25) introduces a kink into DNA, determining start and direction of transcrip.
- TBP binds to TATA box, facilitating binding of other transcrip. factors and RNA poly.

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326
Q

What is the role of Transcription factor II D (TFIID) in transcrip, and relationship with TATA box?

A

1st general transcrip. factor to bind to promoter
- binds to TATA box through TBP - required for all Pol II transcribed genes

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327
Q

Where does RNA poly. II bind in transcrip.?

A

Specific promoter at position (0)

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327
Q

At which nucleotide does transcrip. begin, and what is this position called?

A

Begins at nucleotide +1
- Transcription Start Site

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328
Q

What is the role of Helicase in transcrip.?

A

Catalyses unwinding of DNA during transcrip, leading to DNA chain separation

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329
Q

What is the key event during Initiation phase of transcription, and what is required for this step?

A

Selection of 1st nucleotide of growing RNA
- requires additional general transcrip. factors

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330
Q

What occurs during Elongation phase of transcription?

A

Addition of further nucleotides to RNA chain in 5’→3’ direction

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331
Q

What is the purpose of the Termination phase in transcription?

A

Release of finished mRNA molecule

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332
Q

What is the primary function of Splicing during mRNA processing?

A

Removes introns (non-coding regions) from premature mRNA to create mature mRNA containing only exons (coding regions)

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333
Q

What is added to the 3’ end of premature mRNA during processing?

A

Poly-adenosine tail
- aka: poly-A tail

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334
Q

What is added to the 5’ end of premature mRNA during processing?

A

5’ cap

335
Q

What occurs during the Initiation phase of translation, and what provides the energy for this process?

A

Formation of an initiation complex
- provided by GTP (guanosine triphosphate)

335
Q

What happens during Elongation phase of translation, and how are amino acids attached to their corresponding tRNA molecules?

A

Anticodons of tRNA form base pairs with codons on mRNA.
Aminoacyl-tRNA synthetases catalyse covalent attachment of amino acids to their corresponding tRNA molecules

336
Q

What happens during Termination phase of translation and the events that lead to the release of the protein?

A
  • occurs when the A site encounters a stop codon. Termination protein binds to codon, causing ribosome to dissociate - change in peptidyl transferase activity, resulting in release of protein from the last tRNA to which it was attached
336
Q

What are some examples of post-translational modifications in protein processing?

A
  • Glycosylation
  • Disulphide bods (ER)
  • Folding/assembly of multi-subunit proteins (ER)
  • Specific proteolytic cleavage (ER, Golgi, secretory vesicles)
336
Q

What processes occur during peptide bond formation and translocation in translation, and what is the role of EF-2?

A

Peptidyl transferase catalyses peptide bond formation between amino acids in P and A sites
- EF-2 (Elongation Factor-2) moves ribosome along mRNA

337
Q

What are the 3 tRNA binding sites on a ribosome, and in what order do tRNAs move through them during translation?

A
  • P (peptidyl site)
  • A (acceptor site)
  • E (exit site)
    In translation: PAE
338
Q

Where are Free Ribosomes located, and what do they produce?

A

In cytosol
- produce proteins for the cytosol, nucleus, mitochondria - are synthesised post-translationally (produced in cytosol then translocated (after translation))

339
Q

Where are Bound Ribosomes located, and what do they produce?

A

On Rough Endoplasmic Reticulum (ER)
- produce proteins for plasma membrane, ER, Golgi, secretion - are synthesised co-translationally, with translocation occurring concurrently with translation.

340
Q

Translocation vs Translation?

A
  • Translocation: movement of materials within a cell/organism
  • Translation: protein synthesis in which amino acids are assembled into a protein based on the info provided by messenger RNA (mRNA)
341
Q

What are Point mutations?

A

Change in a single base in DNA sequence

342
Q

What is a Missense mutation?

A

Change in amino acid sequence

343
Q

What is a Nonsense mutation?

A

Creates new termination codon (stop codon) in DNA sequence, terminating protein synthesis

344
Q

What is a Silent mutation?

A

No change of amino acid sequence even though base in DNA altered

345
Q

What is a Frameshift mutation?

A

Addition/deletion of 1 or 2 bases which changes reading frame of translation, potentially altering entire amino acid sequence

346
Q

What are Chromosomal Mutations, and how do they affect genome?

A
  • Genetic changes that affect larger portions of genome, including: Deletions (loss of genetic material), Duplications (extra copies of genetic material), Inversions (reversal of genetic material), Dislocations (translocation of genetic material to a different chromosome)
347
Q

What are the key features of the genetic code?

A
  • Degenerate (multiple codons can code for the same amino acid)
  • Unambiguous (each codon codes for a specific amino acid)
  • Near-universal (it’s shared by most living organisms)
348
Q

What is meant by Specificity of enzymes?

A

The ability of an enzyme to select a specific substrate from a range of chemically similar compounds

349
Q

How do enzymes affect the rate of a chemical reaction?

A

Speed up rate of reaction by binding to and stabilising transition state, reducing activation energy, and providing alternative reaction pathway

350
Q

What is Potency of enzymes, and how does it relate to their function?

A

Can convert many substrate molecules into products per second
- making them efficient catalysts for chemical reactions

351
Q

What type of enzyme catalyses phosphorylation reactions?

A

Kinase enzymes

351
Q

What are Cofactors, and what are examples?

A

Required for enzymatic activity and can be metal ions. - essential for enzyme function
- metals (e.g. magnesium, copper) or organic compounds (e.g. heme, sugars, proteins)

352
Q

What are Coenzymes, and how do they differ from cofactors?

A

Organic molecules, such as vitamins, required for enzymatic activity
- transiently associate with the enzyme, change charge or structure during the reaction, but are regenerated for further use

352
Q

What are Prosthetic groups?

A

Tightly bound coenzymes that remain closely associated with enzyme

353
Q

Apoenzyme vs Holoenzyme?

A
  • Apoenzyme: enzyme without cofactor
  • Holoenzyme: enzyme with cofactor
354
Q

Where does the substrate bind in an enzyme?

A

Active site
- contains amino acids for catalytic activity and specific interactions

355
Q

What does the Lock and Key model describe?

A

Active site of unbound enzyme is complementary in shape to substrate, allowing them to fit together

356
Q

Examples of active sites in enzymes and their specific interactions?

A
  • Chymotrypsin: has hydrophobic pocket that binds aromatic amino acids
  • Trypsin: has negatively charged Asp that interacts with positively charged Lys or Arg.
  • Elastase: has active site partially blocked, allowing only amino acids with small/no side chains to bind
357
Q

What is the Induced Fit model of enzyme-substrate interaction?

A

Binding of substrate induces conformational change in enzyme, resulting in complementary fit between enzyme and substrate

357
Q

How do temperature and pH affect enzyme activity?

A

Each enzyme has an optimum temperature and pH, and activity decreases on either side of this optimum
- extreme temperature/pH alter enzyme’s active site and reduce its function

357
Q

What are Isozymes?

A

Enzymes that catalyse the same reaction but have different properties and structures

358
Q

In what ways can Isozymes differ?

A
  • Synthesised during different stages of fetal and embryonic development
  • Being present in different tissues
  • Located in different cellular locations
358
Q

Example of tissue-specific isozymes and their roles?

A

Lactate Dehydrogenase (LDH) has tissue-specific isoforms, such as H (heart) that promotes aerobic metabolism, M (muscle) that promotes anaerobic metabolism. LDH found in blood is associated with hypoxia

359
Q

How can enzyme activity be regulated by phosphorylation?

A

Activity can be activated/inactivated through addition/removal of phosphate groups by kinases and phosphatases

360
Q

What are Zymogens (proenzymes)?

A

Inactive precursors of enzymes - transformed into active enzymes by cleavage of covalent bonds

361
Q

Example of Zymogens and their activation process?

A
  • In pancreas: Trypsinogen and Chymotrypsinogen are inactive precursors formed
  • In small intestine: Enteropeptidase cleaves Trypsinogen to form active Trypsin, which cleaves Chymotrypsinogen to form active Chymotrypsin
362
Q

What is Michaelis-Menten Kinetics used to describe?

A

The rate and mechanism of enzyme-catalysed reactions:
V = V max [S] / KM + [S]

362
Q

What does [S] represent?

A

Solute (substrate) concentration

363
Q

What does V0 mean?

A

Initial velocity (rate) of an enzyme-catalysed reaction

363
Q

What does VMAX mean?

A

Max. rate of reaction when all enzyme active sites are saturated with substrate
- represents enzyme’s maximal catalytic capacity

363
Q

What is Km (Michaelis constant)?

A

Substrate conc that results in half max velocity (0.5 * VMAX)
- reflects enzyme’s affinity for substrate

363
Q

What does a low Km value indicate about enzyme behaviour?

A

Enzyme requires low substrate conc to work at half max velocity
- indicating high affinity for substrate

363
Q

What does a high Km value indicate about enzyme behaviour?

A

Enzyme requires high substrate conc to work at half max velocity
- indicating low affinity for substrate

363
Q

Km Formula?

A

Км = k _1 + K2 / k1

363
Q

What does K -1 indicate?

A

Rate of enzyme dissociation from substrate, which is Backward rate of reaction

363
Q

What does K2 indicate?

A

Forward rate at which enzyme converts substrate into product

363
Q

What does K1 indicate?

A

Forward rate at which enzyme associates with substrate

364
Q

What is the significance of VMAX in a Lineweaver-Burk Plot?

A

Where line intersects Y-axis
- represents max rate of enzyme-catalysed reaction

364
Q

What does KM indicate in a Lineweaver-Burk Plot?

A

Where line intersects X-axis
- represents substrate conc at which reaction rate is half of VMAX

364
Q

How does a small change in substrate conc affect the reaction when the enzyme’s KM is near physiological conditions?

A

Large change in reaction rate (V)
- indicating high sensitivity to substrate changes

364
Q

What happens to the reaction when KM is much smaller compared to physiological conditions?

A

Little effect on reaction rate

364
Q

What is Competitive Inhibition?

A

Molecule binds to active site of enzyme, competing with substrate for binding

364
Q

How does Competitive Inhibition affect VMAX and Km?

A
  • VMAX same
  • Km (Michaelis constant) changes
364
Q

What is Non-Competitive Inhibition?

A

Molecule binds to allosteric site on enzyme, not active site

364
Q

How does Non-Competitive Inhibition impact VMAX and Km?

A
  • VMAX changes
  • Km same
364
Q

What is Feedback Inhibition?

A

Where end product of metabolic pathway inhibits an earlier enzyme in pathway through allosteric control

365
Q

What is a Suicide Inhibitor?

A

Substrate that remains covalently bound to enzyme’s active site
- enzyme permanently inactive

365
Q

What characterises Non-Competitive Irreversible Inhibition?

A

Formation/breakage of covalent bonds within enzyme complex

366
Q

How does Allosteric control work in enzyme regulation?

A

Involves inhibition of rate-limiting enzymes by end products
- results in sigmoidal curve. Eg: binding oxygen to haemoglobin

366
Q

What is a Mutation?

A

Any heritable change in human genome causing genetic disorder

367
Q

What are Polymorphisms?

A

Variations in human genome with population frequency >1%
- don’t cause disease on their own but may predispose to common diseases

367
Q

What does Penetrance measure?

A

Likelihood of having a disease if you have gene mutation

368
Q

What does Expression refer to?

A

Variation in phenotype (observable traits) if you have a disease

369
Q

What characterises classical genetic diseases (Mendelian disorders)?

A

Require just one mutation to cause disease
- high penetrance
- small environmental contribution

369
Q

What defines Multifactorial diseases?

A

Multiple polymorphisms collectively contribute to the risk of disease
- penetrance for any one mutation is low

370
Q

What does a mutation in the promoter region do?

A
  • Stops transcription
  • Causes abnormal splicing
370
Q

How does altering splice consensus affect gene expression?

A
  • Stops transcription
  • Causes abnormal splicing
371
Q

What are the consequences of a base change creating a new stop codon?

A
  • Leads to a short/absent protein
  • mRNA decay
372
Q

What happens when a base change alters the amino acid sequence?

A

Results in a different or non-functioning protein

373
Q

What does an insertion or deletion mutation do to amino acid sequence?

A

Complete change to the amino acid sequence after the mutation site

374
Q

What is the difference between “in frame” and “out of frame” insertion/deletion mutations?

A
  • “In frame”: insertion/deletion of a multiple of 3 bases
  • “Out of frame”: results in frameshift mutation
375
Q

What are the key components of genetic nomenclature?

A
  • G: genomic build
  • C: describes effect on mRNA sequence (e.g: c.125[C>G])
  • P: indicates effect on peptide sequence (e.g., p.Pro172Arg)
  • > : signifies substitution of bases
  • Ins/Del: insertion/deletion mutations (e.g., c.76insG)
  • c.267+2: indicates substitution within intron
376
Q

How are different genetic mutations described using this nomenclature?

A

c.267G>A represents a substitution.

c.267delG signifies a deletion.

c.267InsA denotes an insertion of an A.

c.267+2T>A describes a substitution within an intron.

377
Q

What does Translocation involve?

A

Rearrangement of chromosomes

377
Q

What characterises Robertsonian translocation?

A

Fusion of 2 acrocentric chromosomes stuck end to end

378
Q

What is Reciprocal translocation?

A

Exchange of genetic material between 2 non-homologous chromosomes

379
Q

What is the key feature of Balanced chromosome rearrangement?

A

all chromosomal material is present
- doesn’t result in visible phenotype, but risk of malsegregation during pregnancy

379
Q

What is the key feature of Unbalanced chromosome rearrangement?

A

Extra/missing chromosomal material, involving 1 or 3 copies of genes
- major developmental problems/miscarriages

380
Q

What is Aneuploidy?

A

Presence of abnormal number of chromosomes, either with extras or missing ones
- X chromosome aneuploidy better tolerated due to X chromosome inactivation

381
Q

What characterises Insertions and Deletions?

A

Missing/duplicated genetic material

382
Q

Why are specific karyotypes important?

A

Identify certain genetic conditions

383
Q

What genetic condition is represented by the karyotype 47XY +21?

A

Down’s syndrome

384
Q

What genetic condition is associated with a karyotype of 45X?

A

Turner syndrome

385
Q

What do the karyotypes 47XY +18 and 47XY +14 suggest?

A

+18: Edwards syndrome
+14: Miscarriage

386
Q

What genetic condition is linked to a karyotype of 47XXY?

A

Klinefelter syndrome

387
Q

What is the purpose of PCR in genetic analysis?

A

Amplifies small piece of human genome from patient, allowing detection of mutations in that specific region

387
Q

What is the primary purpose of Array CGH (aCGH)?

A

Find missing/duplicated pieces of chromosomes and polymorphisms
- first-line chromosome test and examines 3 million base pairs. However, doesn’t detect balanced rearrangements

387
Q

What does FISH stand for, and what does it aim to identify?

A

Fluorescence in Situ Hybridisation
- identify evidence of translocations/deletions by using fluorescent probes to stain pieces of chromosomes

388
Q

What is the difference between Whole Exome Sequencing and Whole Genome Sequencing?

A
  • Whole Exome sequencing: focuses on sequencing all exons (protein-coding regions)
  • Whole Genome sequencing: both exons and introns
389
Q

Why is genetic filtering important in genomic analysis?

A

Identify polymorphism variants by removing those unlikely to be disease-causing

390
Q

What is Somatic Mosaicism?

A

Presence of 2 genetically distinct populations of cells, resulting from post-zygotic mutation

390
Q

Example of Somatic Mosaicism?

A

Mosaic Down syndrome
- some cells have 46 chromosomes, while others have 47 chromosomes

390
Q

Does Somatic Mosaicism affect the entire body?

A

NO
- affect portion of body

391
Q

Is Somatic Mosaicism inherited by the next generation?

A

NO

391
Q

How can Somatic Mosaicism for a chromosomal abnormality contribute to cancer?

A

Activate oncogene/delete tumor suppressor gene

392
Q

What characterises a Mendelian disorder?

A

High penetrance, monogenic diseases that follow Mendel’s laws of inheritance
- autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, mitochondrial, Y-linked

392
Q

What are examples of non-Mendelian monogenic disorders?

A

Conditions related to methylation, imprinting, mitochondrial mutations, mosaicism

393
Q

How is Autosomal Dominant inheritance defined?

A

1 faulty gene
- all generations in family affected
- 50% chance of passing the mutated gene to each child if one parent is a carrier

394
Q

How is Autosomal Recessive inheritance defined?

A

2 faulty genes
- all generations in family affected
- 25% chance of passing the mutated gene to each child if both parents carriers

395
Q

Why might a Female carrier show mild symptoms in X-linked inheritance?

A

Random X inactivation
- where half of cells will have faulty gene

395
Q

What is X-linked inheritance?

A

Gene fault located on X chromosome
- X-linked Recessive: females with one pathogenic allele and one normal allele don’t show major clinical features, but males with a single faulty allele are fully affected

395
Q

How does Mitochondrial inheritance work?

A

Transmitted maternally, in ovum
- Mutations in mitochondrial genome are only present in some mitochondria, and proportion varies between cells within an individual

396
Q

What characterises Multifactorial diseases?

A

Complex interplay of multiple genes and environ. factors

397
Q

What are the possible outcomes when a carrier Female has children in X-linked Recessive inheritance?

A

25% each:
- unaffected or affected son, unaffected or carrier daughter

397
Q

What happens when an affected Male has children in X-linked Recessive inheritance?

A
  • All daughters will be carriers
  • All his sons will be unaffected (no male-male transmission)
398
Q

What is the concept of Precision medicine in multifactorial diseases?

A

Tailoring medical interventions to genetic makeup

399
Q

What are the components of a Prokaryotic cell?

A
  • Plasma membrane
  • Cell wall
  • Nucleoid
  • Ribosomes
  • Cytoplasm with lipid bilayer
400
Q

What is the primary role of the Cytoplasmic membrane in bacteria and why is it a target for antimicrobial agents, such as ethanol?

A

Essential for energy generation, maintaining positive charge
- Target because: electrons released from high-energy compounds in cytoplasm pass through series of electron acceptors at membrane, disrupting bacterial energy production

401
Q

What is the Nucleoid in prokaryotic cells, and how does it differ from eukaryotic cells?

A
  • contains DNA and associated proteins
    Unlike eukaryotic cells, no nuclear membrane, histones, or nucleus exist.
    Chromosomes in prokaryotes are single, circular molecules and are organised by Gyrases.
    Ribosomes in prokaryotes are distinct from eukaryotes and susceptible to interference from drugs that don’t affect eukaryotic ribosomes
402
Q

What is the role of the Peptidoglycan cell wall in bacteria?

A

Provides protection to bacterial cells

403
Q

What are the characteristics of the peptidoglycan cell wall in Gram-POSITIVE bacteria?

A
  • Multi-layered peptidoglycan layer, contain second polymer
  • Resistant to osmotic pressure
  • STAIN PURPLE
404
Q

What are the characteristics of the peptidoglycan cell wall in Gram-NEGATIVE bacteria?

A
  • Thinner peptidoglycan layer
  • Decorated with inner and outer membranes
  • STAIN PINK
405
Q

What is Lipopolysaccharide (LPS) and its functions?

A

Key component of endotoxin found in outer membrane of Gram-negative bacteria
- acts as antigen and bacterial toxin
- roles in antibiotic uptake, inflammation

406
Q

What are Flagella and Fimbriae?

A
  • Flagella: hair-like structures found in Gram-negative bacteria
  • Fimbriae (or pili): found in Gram-positive bacteria
407
Q

What is the role of Flagella and Fimbriae?

A

Allow horizontal gene transfer (HGT) and facilitate the transfer of plasmids between prokaryotes
- inject toxins into host cells and other bacteria

408
Q

What initiates the energy generation process in prokaryotes?

A

Electrons are released from high-energy compounds in cytoplasm

409
Q

How are electrons utilised in prokaryotes for energy generation?

A

Electrons passed through series of electron acceptors after reaching the cell membrane

410
Q

What is the role of Protons in energy generation in prokaryotes?

A

Protons outside membrane create positive charge and a proton gradient, which is used by ATP synthase for ATP synthesis

411
Q

What are the key factors that influence bacterial growth?

A
  • Food availability
  • Temperature
  • pH
412
Q

How does temperature affect bacterial growth?

A
  • Thermophiles: thrive in HIGH temp
  • Mesophiles: thrive at BODY temp
  • Psycrophiles: thrive in LOW temp

Fever: response to infection, raises temp above mesophiles

413
Q

How does pH affect bacterial growth?

A

Affecting acidity/alkalinity of environ

414
Q

How can osmotic protection be provided to bacteria?

A

Provided by a 0.85% NaCl (salt) solution

414
Q

How does Oxygen affect bacterial growth?

A
  • Aerobes: won’t survive in anaerobic conditions
  • Micro-aerophiles: require little free oxygen
  • Facultative anaerobes: can grow with/without oxygen
  • Obligate anaerobes: only grow in anaerobic conditions
  • Caponphilic: require CO2
415
Q

What are Biofilms in context of multicellularity?

A

Colonies of bacteria that adhere together and to environ surfaces.

  • Bacteria inside biofilm more resistant to antimicrobial agents
415
Q

What is the outermost layer found in many bacteria, and what is it usually made of?

A

Capsule
- made of polysaccharides

416
Q

What are Cocci, and what are some examples?

A

Spherical bacterial shapes

Examples:
- Staphylococcus (forming clumps)
- Streptococcus (arranged in chains)

417
Q

What are Bacilli, and how do gram-positive bacilli often appear?

A

Rod-shaped bacteria
- Gram-positive bacilli appear in chains

418
Q

What are 2 primary categories of Spiral-shaped bacteria, and how do they differ?

A
  • Spirillum (rigid spirals)
  • Spirochaete (flexible spirals)
419
Q

What are Vibrio bacteria, and what is their typical shape?

A

Curved rod shape
- Gram-negative

420
Q

Describe the shape of Fusiform bacteria

A

Spindle-shaped appearance

421
Q

What are Bacterial Spores, and what is their primary characteristic?

A

Inert structures highly resistant to physical/chemical damage.
They are inactive but can persist in environ. and later initiate infections.
- associated with Gram-positive organisms

422
Q

How are Spores produced?

A

Germination → binary fission → sporulation → cell lysis → spore secretion

423
Q

What is the Gram stain used for?

A

Distinguish bacteria based on cell wall structure

424
Q

“Gram-positive bacteria retain the stain due to their thick peptidoglycan layer, while Gram-negative bacteria don’t retain the stain.” TRUE/FALSE

A

TRUE

425
Q

What are the limitations of the Gram stain?

A

Bacteria may have a resistant cell wall that doesn’t take up the stain
- Eg: Mycobacterium tuberculosis (TB) and Treponema pallidum ( spirochaete organism causing syphilis), don’t stain well

426
Q

What are the 2 main categories of microorganisms based on their oxygen requirements?

A
  • Aerobes
  • Anaerobes
427
Q

What is the defining characteristic of Aerobic microorganisms?

A

Grow in presence of oxygen

428
Q

What is an Endotoxin, and which type of bacteria is it associated with?

A
  • Gram-Negative bacteria
    part of G-Negative bacterial cell wall
429
Q

What is an Exotoxin, and which type of bacteria is it produced by?

A

Produced by Gram-Positive bacteria. Generated inside bacterial cell and then exported from it

430
Q

What are the steps to identify micro-organisms?

A
  • Growth in differential media
  • Obtain single colony
  • Pass to automated biochemical processing
431
Q

What is the role of 16S rRNA in bacterial identification?

A

Component of the Holoenzyme, serves as a molecular clock and a fingerprint of species for bacterial identification

431
Q

What colony characteristics are considered during bacterial identification?

A

Size, colour, mucoid appearance, and odour
- For Streptococcus spp, haemolytic characteristics (alpha, beta, gamma) can aid in identification.

432
Q

What is Microbiome?

A

Collection of all microbes, such as bacteria, fungi, viruses, and their genes, that naturally live on our bodies and inside us

433
Q

What is a Pathogen?

A

Harmful organism that can cause disease in a host

434
Q

What is a Commensal organism?

A

Organism part of the normal flora
- mutualistic relationship, where both host and organism benefit
- Endogenous relationship (naturally occurring)

434
Q

Define “Pathogenicity”

A

Ability to cause disease/infect host

435
Q

What is “Virulence”?

A

Severity of disease in host

435
Q

What is the Coagulase Test used for?

A

Differentiate between Staphylococcus aureus and coagulase-negative Staphylococcus species

436
Q

How can the Coagulase Test help identify Staph. aureus?

A

If Coagulase Test is positive (coagulase is present), indicates Staph. Aureus, appears GOLDEN

437
Q

What is an Opportunistic pathogen?

A

Causes problems in immunocompromised patients

438
Q

What is a Contaminant?

A

Grows in culture by accident

439
Q

What does a Negative result in the Coagulase Test indicate?

A

Organism is not Staph. aureus but another Staphylococcus species, including Staphylococcus epidermis

440
Q

What does “α haemolysis” signify?

A

PARTIAL haemolysis, resulting in GREENing of colonies.
- associated with Streptococcus pneumoniae + viridans

440
Q

What is Haemolysis?

A

Used to differentiate between Streptococci

441
Q

What does “γ haemolysis” signify?

A

NO haemolysis
- associated with Enterococcus

441
Q

What does “β haemolysis” signify?

A

COMPLETE haemolysis
- YELLOW
- associated with Group A (pyogenes) and B Strep

441
Q

What causes “Partial haemolysis” in Streptococci?

A

Caused by enzymes that denature haemoglobin inside RBCs

442
Q

What causes “Complete haemolysis” in Streptococci?

A

Caused by enzymes that lyse (rupture) cell wall of RBCs

443
Q

What is the most common cause of Bacterial Meningitis among Gram-negative streptococci?

A

Neisseria meningitidis

444
Q

What does Neisseria Gonorrhoeae cause?

A

Gonorrhea

445
Q

What type of microorganisms are often associated with the GI tract?

A

Gut commensal coliforms

446
Q

What are Coliforms, and how can they cause infections?

A

Gram-negative bacilli
- cause serious infections if they enter normally sterile sites, such as UTIs

447
Q

What is the first-line antibiotic for treating infections caused by coliforms?

A

Gentamicin

448
Q

What is released from the Gram-negative cell wall of coliforms when they die, leading to sepsis?

A

Endotoxin (LPS)

449
Q

How are coliforms differentiated from each other?

A

Based on O antigens (cell wall LPS) and H antigens (flagella)

450
Q

What is Sepsis, and how does it affect the body?

A

Host response to immune infection, and can lead to small blood vessels becoming leaky, decreased blood volume, poor tissue perfusion, increased blood clotting, and increased risk of hemorrhage

451
Q

Why do patients with coliform infections become unwell in the context of sepsis?

A

Endotoxin is released from Gram-negative cell wall when bacteria die, contributing to sepsis

452
Q

What are the steps involved in the development of fever?

A
  1. Antigen/LPS interacts with macrophages
  2. Macrophages release cytokines into the bloodstream
  3. Cytokines travel to anterior hypothalamus
  4. Prostaglandin E is released, increasing the body’s thermal set point
  5. The body perceives it as cold and starts to shiver
  6. Fever occurs
453
Q

How are Streptococcus species identified, and what are some important diseases associated with them?

A

Identified by Haemolysis (rupture/destruction of RBCs)
- Group A Streptococcus (GAS): Scarlet fever, Impetigo
- Streptococcus pneumoniae: causes pneumonia

453
Q

What are non-haemolytic Streptococci, and can you name some examples?

A

Enterococci: Enterococcus faecalis, Enterococcus faecium

453
Q

What are the characteristics of Staphylococcus epidermidis, and where is it commonly associated with infections?

A

Nosocomial (hospital-acquired) pathogen associated with foreign devices like catheters
- coagulase-negative

454
Q

What are the key features of Staphylococcus aureus, and what types of infections is it commonly associated with?

A

Most common cause of skin, soft tissue, and wound infections.
- Coagulase-positive, appears golden in colour, and associated with both nosocomial and community-acquired infections
- Lead to sepsis and has a characteristic clump-forming appearance, resembling grapes

454
Q

What is Enterococcus, and what role does it play in infections?

A

Associated with enteric infections and is part of normal bowel flora. It can cause problems when it enters normally sterile areas

455
Q

What is notable about Clostridioides, and what infections can it cause?

A

Gram-positive anaerobic bacillus that is part of normal bowel flora
- produces exotoxins that can cause severe tissue damage. Clostridium difficile, a species of Clostridioides, is responsible for antibiotic-associated diarrhoea, especially in the elderly. It proliferates in the absence of normal flora.

456
Q

What is the cause of acute inflammation of the lungs?

A

Inhaled pneumococci of the species Streptococcus pneumoniae

457
Q

What does the term “genome” refer to?

A

Can be DNA or RNA, single or double-stranded, linear or circular
- carries genetic information of virus

458
Q

What is the role of a protein capsid in a virus?

A

Protects the viral genome from the environ and helps deliver the genome into host cell

458
Q

What is a Virus Envelope?

A

Lipid bilayer that contains viral proteins
- present only in some viruses

458
Q

What is Icosahedral Symmetry in viruses?

A

Structure consisting of repeated subunits that make up equilateral triangles, arranged in a symmetrical fashion

459
Q

What is Helical Symmetry in viruses?

A

Virus is made up of a single repeated unit, typically forming a spiral or helical shap

459
Q

What are the main structural components of SARS-CoV-2?

A
  • Spike (S)
  • Membrane (M)
  • Envelope (E)
  • Nucleocapsid (N)
459
Q

What are the types of viral spread within a host?

A
  • Neural spread (e.g. herpes simplex virus)
  • Hematogenous spread (e.g., through the blood, as seen in HIV).
459
Q

What are the key steps in viral replication and disease progression?

A
  1. Viral replication: involves gene expression and gene replication
  2. Attachment: virus interacts with specific receptors on target cell
  3. Entry: virus enters cell, often through endocytosis
    For respiratory viruses, entry can occur through inhalation or touch
  4. Uncoating: viral nucleic acid is released from the capsid
  5. Nucleic acid and protein synthesis: host ribosomes are used, along with host polymerases, to produce new viral proteins
  6. Assembly: nucleic acids and proteins are packaged together to form new viral particles
  7. Release: virus can be released through either budding, where it exits the cell with an envelope derived from the host cell membrane (non-lethal to the cell), or lysis, where the virus accumulates until the cell bursts, leading to cell death.
459
Q

What are the viral factors that can cause damage to the host?

A

Cell lysis, cell-cell fusion (sharing cytoplasm), inhibition of host cell transcription and translation (altering cellular function)

459
Q

What are the different ways in which viruses can persist within a host?

A

Viruses initally be asymptomatic, allowing for easy spread to other hosts - become quiescent with no active replication and reactivate after a period of latency.
Some viruses may remain continually active, leading to chronic infections

460
Q

How can viral infections be diagnosed?

A

PCR, Antigen test
- Host response and serology assessed using antibody tests

460
Q

What is the Innate Immune System?

A

Defense mechanism present from birth, providing rapid response

Includes: physical barriers (epithelium, cilia), chemical barriers (lysozyme, low pH)

460
Q

What are the methods for controlling viral infections?

A
  • Targeting antiviral agents, such as reverse transcriptase inhibitors in the case of HIV
  • Vaccination
460
Q

What are the benefits of a Balanced immune system?

A

Provides protection from pathogens while minimising the risk of rejecting donor tissue

460
Q

What are the methods used to manipulate the immune system for disease prevention or treatment?

A
  • Immunisation
  • Anti-inflammatory and immunosuppressive drugs
  • Cancer immunotherapy (CAR T-cell therapy)
461
Q

What is the Adaptive (Acquired) Immune System?

A

Induced by presence of foreign materials and generates a unique response to each pathogen
- exhibits slower response

462
Q

What is the role of MUCUS in the body’s defence against pathogens?

A
  • Traps bacteria and contains lysozymes and defensins, which directly combat invading pathogens
  • lines body cavities exposed to external environ, such the resp, GI, and urogenital tracts
  • IgA Role
463
Q

What is the role of COMMENSAL BACTERIA in the body’s defense against pathogens?

A

Compete with pathogens for resources and produce fatty acids and bactericidins, inhibit pathogens

464
Q

What are Pathogen-Associated Molecular Patterns (PAMPS)?

A

Molecules found on surface of pathogens like bacteria, viruses, and fungi that trigger innate immune response.
- recognised by Pattern Recognition Receptors (PRRs) on immune cells, leading to immune response to combat the invading pathogens

465
Q

How do Interferons released by virally infected cells affect neighbouring uninfected cells?

A

They signal neighbouring cells to destroy viral RNA, reduce protein synthesis, undergo apoptosis
- activate immune cells like NK cells

465
Q

What is Phagocytosis?

A

Process by which intact particles, such as bacteria, are internalised whole by macrophages

466
Q

What are the steps involved in Phagocytosis?

A
  1. PRRs on macrophages bind to PAMPs on pathogen, signalling formation of phagocytic cup
  2. Cup extends around pathogen and pinches off, creating phagosome
  3. Phagosome fuses with a lysosome, forming a phagolysosome
  4. Pathogen is killed, and its contents are degraded
  5. Debris is released into extracellular fluid
  6. Pathogen-derived peptides are presented on special cell surface receptors like MHC-II
  7. Pro-inflammatory mediators, such as TNF-α, are released, leading to acute inflammation
467
Q

What is Opsonisation, and which factors act as opsonins?

A

Coating of pathogens by soluble factors (opsonins) to enhance phagocytosis
- IgG, C3b

468
Q

Is the Innate immune system SPECIFIC to micro-organisms?

A

YES

469
Q

Is the Adaptive Immune System NON-SPECIFIC to micro-organisms?

A

YES

470
Q

What are the key characteristics of the SKIN as a barrier to infection?

A

Physical barrier - tightly packed, highly keratinised cells
- Low pH (5.5), low oxygen tension,
- contains sebaceous glands that produce hydrophobic oils, lysozymes, ammonia to deter pathogens

471
Q

What are the 2 mechanisms of phagocytosis by neutrophils?

A
  • Phagolysosomal mechanism: where immune cells engulf and digest invading pathogens within specialised compartments (phagolysosomes)
  • ROS-dependent mechanism: use reactive oxygen species (ROS) to attack and destroy pathogens, which helps in the immune response against infections
472
Q

What are the functions of Mast cells?

A
  • Deal with pathogens that are too large for phagocytosis
  • Initiate response when endotoxin damages mast cell
473
Q

What are the 2 primary mechanisms of mast cell activation?

A
  • Degranulation: involves the release of pre-formed pro-inflammatory substances, such as histamine
  • Gene expression: leads to production of new pro-inflammatory substances like leukotrienes and prostaglandins
474
Q

“Granules contain toxic substances which destroy pathogen when granule is released” - TRUE/FALSE

A

TRUE

475
Q

What are the physiological signs of acute Inflammation?

A
  • Vasodilation of small blood vessels
  • Increased blood flow
  • Cell accumulation
  • Increased cell metabolism
475
Q

Characteristics of Healthy Tissue

A
  • No inflammatory mediators
  • Normal vasculature
  • Circulating neutrophils
475
Q

What are the symptoms of acute inflammation?

A
  • Swelling
  • Pain
  • Heat
  • Redness
  • Joint immobility
476
Q

What does Inflammation promote?

A
  • Change in vascular permeability
  • Recruitment and activation of neutrophils (transendothelial migration)
  • Bacteria produce chemicals that attract neutrophils to site of infection
477
Q

How do neutrophils migrate from the bloodstream to site of injury during inflammation?

A
  1. Loss of intravascular fluid in the presence of inflammation causes slower blood flow, allowing neutrophils to undergo margination
  2. Neutrophils travel close to endothelial cells instead of the centre of vessel
  3. Neutrophils encounter and bind to adhesion molecules expressed by endothelial cells (e.g. Selectins, ICAM-1)
  4. Neutrophils migrate across endothelium via diapedesis
  5. Once in tissues, neutrophils travel to exact site of injury via chemotaxis
  6. Neutrophils activated by PAMPs and pro-inflammatory mediators such as TNF⍺
477
Q

What are 3 immune responses involved in killing mechanisms?

A
  1. Phagocytosis: utilises phagolysosomal killing similar to macrophages by producing ROS
  2. Degranulation: involves release of anti-bacterial granules into Extracellular matrix (ECM)
  3. NETs (Neutrophil Extracellular Traps): release a net-like structure that traps pathogens, leading to phagocytosis
478
Q

What are the modes of ingestion used in immune responses?

A
  • Receptor-mediated Endocytosis: molecules bound to membrane receptors are internalised - crucial for generating adaptive immunity
  • Pinocytosis: ingestion of fluid from surrounding cells
  • Phagocytosis: process in which bacteria are engulfed by cell surface
478
Q

What are the key characteristics and functions of Basophils?

A
  • Contain granule: release histamine
  • act as effector cells in allergic reactions
479
Q

What is the role of Natural Killer cells in the immune system?

A
  • Kill infected/abnormal cancer cells
  • Lymphocytes involved the rejection of tumors and virally infected cells
  • Respond to levels of MHC class I
  • Kill targets by degranulation, releasing perforin
  • Produce Interferon-gamma (IFN𝛾)
479
Q

What is the association between Eosinophils and Allergies?

A

Associated with allergic reactions

480
Q

How can Innate immune response be enhanced?

A
  • Boosted by antibodies
  • The complement system, particularly the classical pathway activated by IgM and IgG, plays role
  • TNF-alpha initiates inflammation
  • Dendritic cells capture antigens and deliver them to lymph nodes
481
Q

How do Macrophages recognise pathogens quickly?

A
  • Use surface molecules such as PAMPs (pathogen-associated molecular patterns)
  • Contain components from bacterial and fungal walls
  • For intracellular pathogens like viruses, PAMPs can be RNA or DNA
482
Q

What are the Functions of Macrophages?

A
  • Phagocytise dead cells and invading pathogens
  • Distinguish between self-cells and pathogens based on their cell surface characteristics
  • DON’T distinguish between different types of pathogens
483
Q

What are various Immune Cells?

A
  • Macrophages
  • Neutrophils
  • Eosinophils
  • Basophils
  • Mast cells
483
Q

What do PAMPs stand for, and what do they do?

A

Pathogen-Associated Molecular Patterns
- recognised by Pattern Recognition Receptors (PRRs)
- specific molecular patterns on pathogens that PRRs detect

484
Q

What are Phagocytic PRRs, and when do they activate?

A

Receptors on immune cells that can activate when there are few pathogens present

  • bind to PAMPs, allowing phagocytes to ingest pathogens
485
Q

When do Signalling PRRs request reinforcements, and what do they stimulate the release of?

A

When there’s a high number of pathogens
- stimulate release of cytokines

486
Q

What are Cytokines?

A

Small secreted proteins that act as messengers, allowing communication between cells in immune response

487
Q

What is the role of Helper T cells in the immune response?

A
  • Involved in the cell-mediated immune response
  • Recognises antigens presented by MHC class II molecules
  • Expresses CD4 - also CD3, TCR & CD28
  • Major source of IL-2
  • Mediates acute and chronic organ rejection
488
Q

What is the function of Cytotoxic T cells in the immune response?

A
  • Involved in the cell-mediated immune response
  • Recognises antigens presented by MHC class I molecules
  • Induce apoptosis in virally infected and tumour cells
  • Expresses CD8 - also CD3, TCR
  • Mediates acute and chronic organ rejection
489
Q

What is the role of B cells in the immune response?

A
  • Major cell of the humoral immune response
  • Act as antigen-presenting cells
  • Mediate hyperacute organ rejection
490
Q

What is the distinguishing feature of Plasma cells?

A
  • Differentiated from B cells
  • Produces large amounts of antibody specific to a particular antigen
491
Q

What is the function of the Kinin system in innate immune responses?

A

Generates proteins that sustain vasodilation and other physical inflammatory effects

492
Q

What is the role of the Coagulation system in innate immune responses?

A

Forms a protective protein mesh over sites of injury

493
Q

What does the Fibrinolysis system do in innate immune responses?

A

Opposition to the Coagulation system
- counterbalancing clotting and generating other inflammatory mediators

494
Q

What is the main function of the Complement system in the innate immune response?

A

Activated in response to inflammation and creates cascade of chem.reactions that promote:

  • Opsonisation of pathogens
  • Direct pathogen killing
  • Acute inflammation
  • Leukocyte recruitment
495
Q

What are the 3 complement pathways?

A
  1. Mannose-Binding Lectin (MBL) pathway
  2. Alternative pathway
  3. Classical pathway
496
Q

How is the Classical pathway of the complement system activated?

A

IgG or IgM antibodies bind to antigens, leading to cleavage of C3 into active C3a and C3b

497
Q

What is the role of C3b in the complement cascade?

A

C3b can cleave C5, resulting in formation of C5a and C5b, leading to production of Membrane Attack Complex (MAC)

  • C3b also amplifies the reaction via alternative pathway
498
Q

What is the function of the membrane attack complex (MAC) in the complement system?

A

Inserts into cell walls and destroys cell by letting salt and water in

499
Q

Which complement components are responsible for acute inflammation and act as anaphylatoxins?

A

C3a, C5a

500
Q

What are acute phase proteins?

A

Produced by the liver that have their plasma concentrations increase or decrease in response to inflammation

501
Q

What is the role of C3 in the complement system?

A
  • C3b: promotes opsonization and enhances phagocytosis
  • C3a and C5a: responsible for acute inflammation
502
Q

What is CRP, and how does it relate to inflammation?

A
  • C-reactive protein
  • acute phase protein that activates complement via classical pathway
  • rapidly increases during inflammation and has a short half-life, decreasing rapidly once inflammation resolves
503
Q

What is the role of MBL in the complement system?

A

Activates the complement system via the MBL pathway in response to inflammation

504
Q

What role do Dendritic cells play in the immune system?

A

Act as a bridge between innate and acquired immune systems

  • capture antigens, deliver them to lymph nodes, and present these antigens to T cells (antigen-presenting cells)
504
Q

Where do B cells mature, and what is their role in the immune response?

A

In Bone Marrow
- responsible for the humoral immune response
- antigen-presenting cells and produce antibodies that attack pathogens in the blood and lymph

505
Q

Describe the route of lymphocytes from lymph nodes to the bloodstream

A

Lymph and lymphocytes leave lymph nodes, enter medullary sinus, flow through efferent lymphatic vessels, and re-enter bloodstream via lymphatic ducts at subclavian vein

506
Q

What cells are associated with Innate immunity?

A
  • Basophils
  • Eosinophils
  • Neutrophils
  • Mast cells
  • NK cells
507
Q

What cells are associated with Acquired (adaptive) immunity?

A
  • B cells (produce antibodies)
  • T cells (TH and Tc cells)
508
Q

What are the 2 signals needed for B cells to fully activate and proliferate upon encountering an antigen?

A
  • Antigen exposure
  • “Helping” signals
509
Q

What do B cells differentiate into after activation?

A

Plasma cells

510
Q

Describe the initial immune response to antigen exposure

A

Low-affinity antigen-specific IgM antibodies are secreted by short-lived plasma cells. These later undergo somatic hypermutation to become high-affinity IgG antibodies. B cells mutate and secrete improved antibodies, switching from low to high-affinity antibody production. This leads to differentiation of long-lived plasma cells and long-lived memory B cells (Bm)

511
Q

What are the types of Passive immunity?

A
  • Naturally acquired passive immunity through IgG (placenta) and IgA (milk)
  • Artificially acquired passive immunity through interventions like antivenom
512
Q

What are the types of Active immunity?

A
  • Naturally acquired active immunity through actual infection by a pathogen
  • Artificially acquired active immunity through vaccines and booster shots involving exposure to weakened/dead pathogens
513
Q

What are the steps in B cell activation and the generation of high-affinity antibodies?

A
  • Membrane-bound antibodies on B cells bind to target antigen (IgM or IgD) in B cell zone of lymph nodes
  • B cells require for activation: antigen and helper signals from T helper (TH) cells, PRR and PAMPs, or multiple antigens
  • Once activated, proliferate and become plasma cells (producing antibodies) or memory B cells, often in germinal centres
  • High-affinity antibodies are generated, starting with IgM (produced by plasma cells) and transitioning to IgG (produced by B cells responding to specific antigens), assisted by TH cells
514
Q

Where do T cells mature?

A

Thymus

515
Q

What type of antigens can T cells recognise?

A

Peptide antigens

516
Q

What is the function of CD4+ Helper T cells?

A

Activate B cells and stimulate production of memory B cells

  • can differentiate into Th1, Th2, Tfh, and regulatory T cells
517
Q

What is the function of CD8+ Killer T cells?

A

Kill virally infected body cells

518
Q

What is the role of Regulatory T cells?

A

Lymphocyte suppression

519
Q

What is the role of Memory T cells?

A

Protective immunity against invading pathogens

  • role in adaptive immune response
520
Q

What is the function of Major Histocompatibility Complex (MHC) molecules?

A

aka: HLA (Human Leucocyte Antigens)
- display peptide antigens to T cells
- T cells can only recognise peptide antigens presented to their T cell receptor (TCR) by MHC molecules

521
Q

Where are Class I MHC molecules expressed, and what is their function?

A

On all nucleated cells

  • present peptide antigens to CD8+ Killer T cells
522
Q

Where are Class II MHC molecules expressed, and what cells are considered professional Antigen Presenting Cells (APCs)?

A
  • Only on professional Antigen Presenting Cells (APCs), including dendritic cells, macrophages, B cells
  • Present peptide antigens to CD4+ Helper T cells
523
Q

Where does antigen presentation activate B cells and T cells?

A

In Secondary lymphoid tissues:
such as lymph nodes, spleen, mucosa-associated lymphoid tissue (MALT)

524
Q

How do mature, quiescent, antigen-specific T cells and B cells move within the body?

A

Constantly re-circulate between the blood, secondary lymphoid tissues, and lymphatic vessels

525
Q

What is the 1st step in T cell activation by dendritic cells?

A

Dendritic cells recognise and phagocytose antigenic debris

526
Q

What happens to dendritic cells in the presence of pro-inflammatory mediators like TNF⍺?

A

Mature and increase the expression of stimulatory molecules on their surface

527
Q

How do dendritic cells prepare antigenic debris for T cell recognition?

A

Dendritic cells phagocytose pathogenic antigens, break them down into short peptides, and load them onto MHC II molecules

528
Q

What happens to MHC II molecules after they are loaded with antigens?

A

Transported to cell surface of dendritic cells

529
Q

Where do maturing dendritic cells migrate, and how do they get there?

A

Migrate into lymph nodes via the afferent lymphatic vessels

530
Q

What enables T cells to respond to antigens and fully differentiate?

A

Co-stimulatory molecules

531
Q

What type of T cells differentiate from CD4+ T cells?

A

CD4+ T cells differentiate into T helper cells, which include effector TH cells

532
Q

What are the 2 main types of T cells produced after antigen contact?

A
  • Memory T cells
  • Effector T cells
533
Q

What is the role of Th0 cells?

A

Release IL-2
- enhances growth and function of both T and B cells

534
Q

What is the role of Th1 cells?

A

Activate macrophages to be more efficient, which includes activation of NADPH oxidase genes to produce reactive oxygen species (ROS)

535
Q

What is the role of Tfh cells?

A

Activate B cells in germinal centre

536
Q

What type of T cells differentiate from CD8+ T cells?

A

CD8+ T cells differentiate into Cytotoxic T lymphocytes (CTLs)

537
Q

Do CTLs kill infected host cells?

A

Bind to infected cells and induce apoptosis
- use granules containing perforin, granzymes, and granulysin to trigger apoptosis

538
Q

How do CTLs enter the site of infection, and what is their role?

A

Migrate out of lymph nodes and enter site of infection via transendothelial migration to kill infected host cells and stop further inflammation

  • Involved in killing cancer cells
539
Q

What types of lymphocytes are generated during lymphopoiesis?

A

B and T lymphocytes, each with its own antigen receptor

540
Q

What is one of the key processes during lymphopoiesis?

A

Getting rid of lymphocytes with self-reactive antigens to ensure self-tolerance and prevent autoimmune reactions

541
Q

Describe IgG

A

Monomer

  • Enhance phagocytosis of bacteria and viruses
  • Fixes complement and passes to fetal circulation
  • Most abundant isotype in blood serum
542
Q

Describe IgA

A

Monomer/Dimer

  • Found in breast milk, secretions of digestive, respiratory and urogenital tracts/systems
  • Provides localised protection on mucous membranes
  • Most commonly produced immunoglobulin (but blood serum concentrations lower than IgG)
  • Transported across interior of the cell via transcytosis
543
Q

Describe IgM

A

Pentamer

  • First immunoglobulin to be secreted in response to infection
  • Fixes complement but doesn’t pass to fetal circulation (result in haemolysis)
  • Anti-A, B blood antibodies
544
Q

Describe IgD

A

Monomer

  • Role in immune system largely unknown
  • Involved in activation of B cells
545
Q

Describe IgE

A

Monomer

  • Mediates Type 1 hypersensitivity reactions
  • Synthesised by plasma cells
  • Binds to Fc receptors found on surface of mast cells and basophils
  • Provides immunity to parasites such as helminths
  • Least abundant isotype in blood serum
546
Q

What are Hypersensitivity Reactions?

A

Immune response that results in bystander damage to the self

547
Q

What is Type 1 Hypersensitivity (Anaphylactic)?

A

IgE-mediated antibody response

  • Onset: seconds
  • production of IgE antibodies upon initial allergen exposure, bind to mast cells + cause degranulation upon re-exposure to allergen
  • Conditions: Anaphylaxis, Atopy (e.g. asthma, eczema, hayfever)
548
Q

What is Type 2 Hypersensitivity (Cell bound)?

A

IgG or IgM binds to antigen on cell surface → complement system activation

  • Onset: seconds/hours
  • Conditions: Goodpasture’s syndrome, Rheumatic fever
549
Q

What is Type 3 Hypersensitivity ( Immune Complex)?

A
  • Antibody binds to excess soluble antigen producing small immune complexes, trapped in small blood vessels, joints and glomeruli → activate complement → attracts inflammatory cells
  • Onset: hours
  • Conditions: Systemic lupus erythematosus, Post-streptococcal glomerulonephritis, Extrinsic allergic alveolitis
550
Q

What is Type 4 Hypersensitivity (Delayed Hypersensitivity)?

A

T cell mediated: release of inflammatory cytokines and cell-mediated cytotoxicity

  • Onset: days
  • Conditions: Tb, Allergic contact dermatitis, Guillain Barre syndrome
551
Q

What is Autoimmunity?

A

Presence of immune responses against self-tissues/cells

552
Q

What are the Genetic contributions to autoimmune diseases?

A
  • IPEX syndrome: results from X-linked mutation in the FOXP3 gene, involved in TREG (regulatory T cell) development
  • Certain HLA (Human Leucocyte Antigen) alleles, which encode for MHC (Major Histocompatibility Complex) cells and are associated with an increased predisposition to autoimmune diseases
  • Autoimmune diseases are more common in females - influenced by hormonal factors
552
Q

What are the 2 categories of tolerance mechanisms in preventing autoimmunity?

A
  • Central tolerance: deletion of self-reactive lymphocytes in primary lymphoid tissues, such as thymus and bone marrow
  • Peripheral tolerance: inactivates self-reactive lymphocytes in peripheral tissues, such as lymph nodes, spleen, tonsils, which may escape central tolerance. TREG cells are involved
552
Q

What are the Environmental contributions to autoimmune diseases?

A
  • Infections that can lead to cross-reactivity (molecular mimicry), where immune response against pathogens may inadvertently target self-antigens
  • Alteration of self-antigens due to processes like the conjugation of self-antigens with products of drug or chemical metabolism
  • The role of super-antigens produced by certain bacteria, which can reactivate autoreactive T cells that have been inactivated by TREG cells
  • Antigen sequestration: occurs when antigens in tissues that don’t normally communicate with the bloodstream or lymphatics (e.g: eye or brain) are exposed due to trauma, leading to an autoimmune reaction
553
Q

The function of the Gastrointestinal epithelial barrier?

A

Serving as physical barrier between host and external environ.

  • consists of single layer of cells and layer of mucus
553
Q

How does GI mucosa play a role in innate immunity?

A

Through secretion of cytokines and antimicrobial peptides, including human defensins, trefoil factors, cathelicidin, REGIIIγ, MUC proteins

554
Q

What does growth dynamics of the epithelial barrier involve?

A

Lgr5+ stem cells located at base of the crypts

  • As these cells proliferate and differentiate, they move up crypt
  • Cell shedding occurs at tip of crypt, maintaining tight control over the barrier through signaling molecules
555
Q

What is Tolerance in the context of the immune system?

A

Immune cells are present in the lamina propria and specialised cell types, including intra-epithelial T cells

  • Self tolerance: development of non-responsiveness to self-antigens, preventing immune system from attacking body’s own tissues
  • Exogenous tolerance: development of non-responsiveness to many newly encountered environmental antigens, such as food and microbes
556
Q

How do intestinal epithelial cells (IEC) interact with microbes in the gut, and what are the consequences

A

They sense and respond to microbes
They express Pattern Recognition Receptors (PRRs), stimulate the secretion of antimicrobial peptides (AMPs), cytokine responses, and regulation of tight junction proteins (TJP), impacting gut permeability

  • influence microbial diversity in gut
  • IECs produce mucins, which serve as energy source for gut microbes
556
Q

“Immune cells play a role in influencing IECs and gut microbiota by promoting barrier repair through release of molecules like IL-22, particularly by innate lymphoid cells (ILCs)” TRUE/FALSE

A

TRUE

556
Q

What are Antibiotics?

A

Drugs used to treat/prevent infections caused by microorganisms

556
Q

What does “Bacteriostatic” mean?

A

Inhibit bacteria growth

557
Q

What does “Bactericidal” mean?

A

Kill bacteria

557
Q

What are the characteristics of an ideal antibiotic?

A
  • Cidial
  • Long half life
  • Appropriate tissue distribution
  • No adverse drug interactions/side effects
  • Oral & parenteral preparations
557
Q

How are antibiotics typically administered and excreted?

A

Administered: intravenously (IV) or, rare cases, intramuscularly (IM)

  • Excreted through: urine, liver, biliary tract, and can be excreted into faeces
557
Q

What are the common targets of antibiotics in bacteria?

A
  • Bacterial cell walls (inhibiting peptidoglycan synthesis)
  • Ribosomes (affecting protein synthesis)
558
Q

Which antibiotics are Bactericidal?

A
  • Penicillins
  • Glycopeptides
  • Cephalosporins
  • Aminoglycosides
  • Nitromidazoles
  • Quinolones
559
Q

Which antibiotics are Bacteriostatic?

A
  • Macrolides
  • Tetracyclines
559
Q

Which antibiotics target bacterial cell wall?

A

Penicillins, Cephalosporins, Glycopeptides

560
Q

What are Penicillins and their mechanism of action?

A

Eg: Flucloxacillin, Amoxicillin, Co-amoxiclav
- β-lactam antibiotics: targeting Penicillin Binding Proteins (PBPs) in bacteria

560
Q

Strengths of Penicillins?

A
  • Safe in pregnancy
  • Few side effects
  • Range from narrow to broad spectrum
561
Q

Weaknesses of Penicillins?

A
  • Patients can be hypersensitive (allergic) and allergy to one penicillin potentially means allergy to all penicillins
  • Rapidly excreted via kidneys and resistance can develop
562
Q

Which penicillin is used for Gram-Positive organisms?

A

Flucloxacillin (IV, Oral)

562
Q

Which penicillin is used for Gram-Positive AND Negative organisms?

A
  1. Amoxicillin (IV, Oral)
  2. Co-Amoxiclav (IV, Oral)
  3. Tazocin (IV only)
563
Q

Which penicillin is used for Gram-Negative organisms?

A

Temocillin (IV only)

564
Q

What are the 3 principal penicillin compounds?

A
  • Benzylpenicillin
  • Phenoxymethyl penicillin
  • Benzathine penicillin
565
Q

What are the key features of Amoxicillin?

A
  • Safe, well tolerated antibiotic
  • Well absorbed when given orally
  • Low binding to plasma proteins & good tissue distribution
  • Effectiveness challenged by spread of beta lactamases (enzyme that destroys beta-lactam ring)
566
Q

What are the key features of Co-amoxiclav?

A

Combination of Amoxicillin and Clavulanic acid

  • CA: beta-lactamase inhibitor, NO antibiotic properties of its own
567
Q

What are the key features of Flucloxacillin?

A
  • IV and Oral
  • Narrow spectrum antibiotic
  • Prescribed for Staph and Strep
  • For skin and soft tissue infections, wound infections, cellulitis
568
Q

What are the key features of Temocillin?

A
  • IV antibiotic with a Gram-Negative spectrum
  • Beta-lactamase-resistant penicillin and used for coliform infections
  • Active against ESBL (Extended Spectrum Beta-Lactamase) producing organisms
569
Q

What are the key features of Cephalosporins?

A

Eg: Cefaclor, Cefadroxil, Cefalexin

  • Inhibit cell wall synthesis & bactericidal
  • Excreted via kidneys and urine
  • More resistant to β-lactamases
  • Few side effects, reduced allergy, safe in pregnancy

Broad-spectrum antibiotics:
- kill normal gut bacteria
- allow overgrowth of Clostridium difficile
- Hospitals avoid use

570
Q

What are the key features of Glycopeptides?

A

Eg: Vancomycin (IV), Teicoplanin (IV)

  • Inhibits cell wall synthesis through different mechanisms
  • Bactericidal
  • Side effects: vancomycin damages kidneys, causes ‘red man syndrome’ (allergy)
  • Excreted via kidneys and urine
  • NO activity against Gram-Negative organisms
571
Q

Name 3 antibiotics that inhibit protein synthesis

A
  • Erthyromycin
  • Doxycylin
  • Gentimicin (most prescribed)
572
Q

What is Selective Toxicity?

A

Antibiotics’ ability to inhibit protein synthesis by attaching to bacterial ribosomes while structurally differing from mammalian ribosomes

  • allows antibiotics to target bacterial cells without harming human cells
573
Q

Are antibiotics that inhibit protein synthesis bacteriostatic or bactericidal?

A

Bacteriostatic
- Exemption: aminoglycosides are bactericidal meaning they directly kill bacteria by binding to ribosomes in a way that is lethal wa

574
Q

Name 3 antibiotic types that inhibit protein synthesis

A
  • Aminoglycoslides
  • Tetracylines
  • Macrolides
575
Q

What are the key features of Aminoglycosides?

A

Eg: Gentamicin

  • Treat severe, life-threatening infections caused by Gram-Negative aerobic organisms
  • Administered IV and have irreversible binding to 30s ribosome, making them bactericidal
576
Q

What are the key features of Macrolides?

A

Eg: Erythromycin - safe in pregnancy

  • Excreted via liver, biliary tract, and into gut
  • Bacteriostatic - useful when infections hide from host immune system
  • Lipophilic: easily pass through cell membranes
577
Q

What are the key features of Tetracyclines?

A

Eg: Doxycycline

  • Inhibit protein synthesis: bind to 30s subunit of ribosome, prevent attachment of tRNA
  • Useful against: intracellular bacteria, atypical bacteria
  • Side effects: destruction of normal intestinal flora, staining of bone/teeth in children under 12
578
Q

When might Clindamycin be used as a treatment for bacterial infections?

A

2nd-line treatment against serious Staphylococcal and Streptococcal infections, especially in patients with penicillin allergies

  • Active against “true” anaerobes
579
Q

What is the typical application of Chloramphenicol in the context of infections?

A

Used for topical treatment of eye infections

580
Q

How are clindamycin and chloramphenicol excreted from the body?

A

Via liver and biliary system

581
Q

Name antibiotics that target bacterial DNA

A
  • Fluroquinolones
  • Metronidazoles
  • Trimethoprim
  • Rifampicin
  • Rifampin
582
Q

What is a key feature of Fluoroquinolones?

A

Exhibit both Gram-Negative and Gram-Positive activity, making them effective against wide range of bacteria

582
Q

How do Fluoroquinolones achieve selective toxicity, not inhibiting human nucleic acids?

A

By targeting metabolic pathways that are absent in humans

  • specifically bind to the A subunit of DNA gyrase, preventing supercoiling of bacterial DNA
583
Q

What is the mechanism of action of Quinolone antibiotics?

A

Eg: Ciprofloxacin

  • Bind to the A subunit of DNA gyrase, preventing supercoiling of DNA, indirectly inhibits DNA synthesis
  • Gram-Negative & Gram-Positive activity
584
Q

Where are Quinolone antibiotics commonly used?

A
  • Urinary tract infections (UTIs)
  • Bone infections
  • Community-acquired pneumonia
585
Q

What is the main concern with the use of broad-spectrum antibiotics like ciprofloxacin?

A

Restricted to reduce risk of Clostridium difficile (C. difficile) infections, especially in elderly patients

586
Q

What is a key feature of Nitroimadazoles?

A

Eg: Metronidazole

  • breaks strands of bacterial DNA, making it effective against anaerobic bacteria and some protozoa
587
Q

Are there any specific interactions or precautions associated with metronidazole?

A

Yes
- interacts with alcohol and should be avoided when consuming alcoholic beverages

588
Q

What is the primary use of Trimethoprim, often used in combination with sulphonamides?

A

Treatment of urinary tract infections (UTIs), especially those caused by bacteria like E. coli

589
Q

How does Trimethoprim exert its antibacterial effect?

A

Inhibits bacterial folic acid synthesis, making it effective against both gram-negative and gram-positive bacteria

590
Q

What are side effects associated with careful prescribing of antibiotics?

A
  • Nausea, Vomiting, Diarrhea
  • Gentamicin: renal and VII nerve damage
  • Ciprofloxacin: cause tendonitis and avoided in pregnant/breastfeeding women
590
Q

“Combine BOTH bacteriostatic & bactericidal antibiotics” TRUE/FALSE

A

FALSE

591
Q

What is the purpose of Empiric prescribing and Targeted prescribing?

A
  • Empiric prescribing: prescribing antibiotics without lab identification, based on the likely pathogen
  • Targeted prescribing: prescribing antibiotics based on lab identification of pathogen.
591
Q

What are high-risk antibiotics with an increased risk of C. difficile infection?

A
  • Cephalosporins
  • Co-amoxiclav
  • Ciprofloxacin
  • Clindamycin
591
Q

What is a Receptor?

A

Class of cellular macromolecules that are concerned specifically with chemical signalling

591
Q

What is Pharmacology?

A

Study of how the function of tissues/ organs is modified by chemical substances

592
Q

What is Selectivity?

A

Ability of a drug to distinguish between different molecular targets within body

593
Q

What’s a Ligand?

A

Substance bound to protein

593
Q

Definition of Pharmacokinetics?

A

What the body does to a drug

593
Q

Definition of Pharmacodynamics?

A

What a drug does to the body

593
Q

Why is drug specificity important in pharmacology?

A

Ensures that a drug acts selectively on a specific receptor/binding site

  • This specificity reduces the likelihood of side effects since the drug only interacts with its intended target, not activating other receptors
  • NO DRUG IS 100% SPECIFIC
593
Q

What is an Agonist?

A

Drug that binds to receptor to produce cellular response

  • Temporarily activate receptors by producing conformational change
  • Possess affinity and efficacy
594
Q

What is an Antagonist?

A

Drug that reduces/inhibits the actions of agonist by binding to same receptor

  • Possess affinity but lack efficacy
595
Q

What is Affinity?

A

How strongly medication binds to its receptor
- higher affinity = higher potency

596
Q

Difference between Potency and Efficacy?

A

P: amount of drug required to produce a desired effect

E: max. response achievable from drug

596
Q

What is the key concept when considering the equilibrium between ligand association and dissociation?

A

When equilibrium is reached, the rate at which ligand-receptor complexes form is equal to the rate at which they dissociate, and this equilibrium is concentration-dependent

597
Q

What does the term “Ka” represent?

A

Measure of the concentration of ligand required to occupy half of the available receptors

  • Lower Ka indicates a higher affinity of the ligand for the receptor
598
Q

What does EC50 represent in a dose-response curve?

A

Conc of drug where 50% of max effect (response) is achieved

  • Smaller EC50 indicates: less medication is needed to reach halfway to the maximum effect, making the drug more potent
599
Q

What is a Partial Agonist?

A

Response is sub-maximal, even when all receptors occupied

600
Q

Which agonist has greater efficacy?

A

Full Agonist

601
Q

What happens in Competitive Antagonism, and how does it affect potency and efficacy?

A

Both agonist and antagonist bind to same (orthosteric) site on receptor

  • Decrease in potency, no effect on efficacy (EMAX)
602
Q

What characterises Non-Competitive Antagonism, and how does it impact efficacy and potency?

A

Agonist binds to allosteric site on receptor, causing change in receptor’s shape that prevents the ligand from binding

  • Decreased efficacy (EMAX), no effect on potency
602
Q

“The greater the degree that the ligand binds to the receptor and the drug is kicked off, the lower the Ka” TRUE/FALSE

A

TRUE

603
Q

How does a Reversible Competitive Antagonist act, and what is its most common effect on a dose-response curve?

A

Competes with agonist for the same binding site on receptor

  • Overcome by increasing conc of ligand

Rightward shift on dose-response curve

603
Q

What is Chemical Antagonism?

A

Antagonist combines in a solution with chemical being antagonised

  • Reduces effective conc of active chemical
603
Q

How does Physiological Antagonism work?

A

2 agonists that produce opposing physiological actions, canceling each other out

  • Eg: adrenaline relaxes bronchial smooth muscle, counteracting bronchoconstriction caused by histamine
603
Q

What is Pharmacokinetic Antagonism?

A

Antagonist reduces conc of the active drug at its site of action through processes such as increased metabolism

  • Eg: phenobarbitone increases hepatic metabolism of the anticoagulant drug warfarin, reducing effectiveness
604
Q

What are the Classifications of Signals?

A
  • Autocrine signals: acting on the cell that produces them
  • Paracrine signals: targets nearby cells
  • Endocrine signals: targets specific cells far away from source (hormones)
604
Q

How are hydrophobic and hydrophilic ligands transported into cells?

A
  • Hydrophobic: unable to freely move through ECM and require carrier proteins to facilitate their entry into cells
  • Hydrophilic: move freely through ECM and bind to surface receptors on cell
605
Q

What are the 3 stages of cell signalling?

A
  1. Reception: receptor binds to ligand
  2. Transduction: receptor protein changes, activates intracellular molecules (second messengers)
  3. Cell Response
606
Q

The 3 Classes of Signalling Pathways…?

A
  • G-protein coupled receptors
  • Enzyme coupled receptors
  • Ion channel receptors
606
Q

What is the response time for Ligand-gated ion channels?

A

Milliseconds

607
Q

What are the steps involved in the functioning of Ligand-gated ion channels?

A
  1. Ligand binds to receptor, leading to
    channel opening
  2. Ions (Ca²⁺, Na⁺, K⁺) flow through channel passively
  3. Ion flow triggers intracellular signalling pathways
607
Q

What is the role of Varenicline in relation to nicotinic acetylcholine receptors (nAChRs)?

A

Inhibits binding of nicotine to nicotinic acetylcholine receptors

  • partial agonist and helps ease nicotine withdrawal symptoms
608
Q

What is the sequence of action for Ligand-gated ion channels (LGCI) when an agonist binds?

A
  1. Agonist binding induces conformational change in receptor
  2. Receptor’s channel opens, providing conduction pathway for ions
  3. Ions flow down their electrochemical gradient. Eg: at nicotinic acetylcholine receptor, Na⁺ ions move out, K⁺ ions move in, resulting in membrane depolarisation and cellular excitation
609
Q

What is the typical response time for G-Protein Coupled Receptors (GPCRs)?

A

Seconds

610
Q

Describe the structure of the G protein associated with GPCRs

A

Peripheral membrane protein composed of 3 polypeptide subunits: ⍺, β, and 𝛾

  • ⍺ subunit holds GTP or GDP
611
Q

How is the signal turned ON when an agonist activates a G-coupled receptor associated with GPCRs?

A
  1. ⍺ subunit leaves G-protein
  2. GDP is exchanged for GTP through guanine nucleotide exchange
  3. Triggers activation of other proteins in signalling pathway
612
Q

How is the signal turned OFF in GPCRs?

A
  1. ⍺ subunit hydrolyses GTP, converting it back to GDP
  2. Deactivates G protein
  3. ⍺ subunit recombines with β𝛾 subunit
612
Q

What are Adrenoceptors?

A

Receptors that are bound and activated by adrenaline and noradrenaline

612
Q

In the context of asthma, how do medications like salbutamol and theophylline interact with GPCRs?

A
  • Salbutamol: binds to B2 adrenoreceptors, leading to bronchodilation - desired effect for asthma
  • Theophylline: used for chronic asthma, but mechanism of action is different
612
Q

Explain the steps involved when adrenaline binds to b2-adrenoreceptors and causes bronchodilation

A
  1. G proteins are activated, and GDP is converted to GTP
  2. Alpha subunit is free to leave G protein and stimulate adenylylcyclase, causing bronchodilation
  3. G proteins recombine with alpha subunit and GTP, deactivating G proteins
612
Q

How long does it typically take for a response to occur in Enzyme-coupled (kinase-linked) receptors?

A

Hours

613
Q

Describe the structure of enzyme-coupled (kinase-linked) receptors

A

Single-pass transmembrane proteins

  • have an enzyme domain that is a kinase, responsible for phosphorylating other molecules
614
Q

How do receptor tyrosine kinases activate themselves to initiate a cellular response?

A

Can’t phosphorylate their own tyrosine side chains

  • To activate themselves, they dimerise, meaning 2 receptor tyrosine kinases bind together. Cross-phosphorylate each other, increasing affinity for their binding sites and initiating a cellular response
615
Q

Where are Nuclear receptors typically found within the target cell?

A

Nucleus

616
Q

What is the result of the activation of Nuclear receptors?

A

Transcription of key proteins

617
Q

Name some common drug targets

A
  • Receptors
  • Enzymes
  • Ion Channels
  • Carrier Proteins
618
Q

What are the 4 fates of drug absorption in the body?

A

Absorption, Distribution, Metabolism, Excretion

619
Q

How does Passive Diffusion occur in drug absorption?

A

Occurs when small, lipid-soluble, non-polar drugs move directly through cell barriers, taking advantage of high conc gradient

620
Q

What types of drugs are typically involved in Facilitated Diffusion during absorption?

A

Larger, water-soluble drugs, and polar drug

  • May exhibit saturation kinetics, which can lead to drug accumulation in compartments and adverse effects
621
Q

What is Active Transport in drug absorption, and what is required for it to occur?

A

Process of moving drugs against their conc gradient using carrier proteins and ATP
- used for water-soluble drugs and can exhibit saturation kinetics

622
Q

How does the Blood-Brain barrier regulate entry of molecules into the brain?

A

Consists of tight junctions between brain and blood vessels supplying the brain

  • These tight junctions regulate passage of molecules into brain
623
Q

What is Endocytosis?

A

Process of bulk uptake of large molecules through cell membrane

  • Drug is encased in a vesicle and released inside cell
624
Q

How does the degree of ionisation of a drug affect its ability to cross the lipid bilayer?

A

Only unionised form can diffuse across lipid bilayer

  • Degree of ionisation depends on drug pKa and local pH
625
Q

What is pH Trapping in drug absorption, and how does it affect weak acids and weak bases?

A

Drugs getting trapped in compartments with specific pH levels

  • Weak bases: better absorbed in acidic environments
  • Weak acids: better absorbed in alkaline environments

Different compartments have different pH levels that affect drug absorption

626
Q

How do Non-polar drugs behave in terms of membrane crossing and metabolism?

A

Lipophilic - easily cross cell membranes to undergo metabolism

627
Q

What are the primary sites of distribution for drugs in the body?

A

Mouth and walls of small intestine: transported to the liver via portal vein for further processing

628
Q

Formula for Volume of Distribution (Vd)?

A

Vd = Dose / Drug Plasma

629
Q

Steps to determine Vd of drug?

A
  1. Administer known dose of drug
  2. Obtain blood sample and separate plasma from RBCs
  3. Measure conc of the drug in plasma ([drug]*plasma)
  4. Calculate Vd using the formula: Vd = Dose / [drug]*plasma
629
Q

How does plasma protein binding, specifically to albumin, affect a drug’s distribution and transport in body?

A

Albumin: most abundant plasma protein, high affinity for hydrophobic drugs

  • Reduces ability for drug to diffuse to target organ and reduces transport to non-vascular components
629
Q

What is the apparent volume of distribution (Vd) of a drug, and how is it related to its distribution in the body?

A

Extent to which drug spreads between plasma and tissue compartments

  • Low Vd: drugs retained in vascular compartments - mostly in plasma
  • High Vd: drugs retained in non-vascular compartments – adipose, muscle etc
630
Q

What is Drug Metabolism?

A

Process of converting a drug into either an active or inactive form within the body

631
Q

What are Prodrugs?

A

Drugs administered in inactive form, which are then metabolised to their active state within body

632
Q

In which organ does the majority of drug metabolism take place, and what are the 2 phases of drug metabolism?

A

Liver

  • Phase I and Phase II
633
Q

What is First-Pass metabolism?

A

Process in which drugs, especially those taken orally, are transported via portal vein to liver before entering systemic circulation

  • In liver, hepatic enzymes metabolise drug, leading to reduction in drug bioavailability
  • IV and IM admin. methods bypass first-pass metabolism
634
Q

What is Bioavailabillity (F) and its formula?

-

A

Amount of drug that reaches systemic circulation for that route of administration

F = Quantity of drug reaching Systemic Circulation (AUC) / Quantity of drug administered (Dose)

635
Q

What is Phase I Metabolism?

A

Changing a drug through oxidation, reduction, hydrolysis

  • result in formation of active and/or toxic drug metabolites.
636
Q

What are the typical enzymatic reactions involved in Phase I Metabolism?

A

Oxidation: facilitated by cytochrome P450 (CYP 450) enzymes - influenced by interactions with other drugs

  • Hydrolytic reactions on ester and amide bonds. An example of drug toxicity related to this phase is seen in conversion of paracetamol to toxic metabolite by P450 enzymes when taken in large doses, overwhelming the detoxification process
637
Q

What is Phase II Metabolism?

A

Process of combining a drug with polar molecules to form a water-soluble metabolite (Conjugate)

  • involves reactive groups produced during Phase I

Conjugation terminates all biological activity of drug, and resulting products are excreted via kidneys.

Unlike Phase I, some drugs, such as codeine, can go directly to Phase II metabolism

638
Q

What is Glucuronidation, and how does it contribute to drug metabolism?

A

Conjugation reaction where naturally present molecules in body, eg: glucose, are added to a drug

-facilitated by enzyme Uridine Diphosphate-glucuronosyltransferase: utilises uridine diphosphate glucuronic acid as cofactor to link drug with glucose, forming water-soluble conjugate that can be excreted

639
Q

How does genetic variability impact drug metabolism? AND What are the consequences of being a poor metaboliser or a rapid metaboliser?

A
  • Poor metabolisers: have genetic variations that lead to slower metabolism of drugs, resulting in higher drug plasma levels - dangerous side effects
  • Rapid metabolisers: have genetic variations that lead to faster drug metabolism, reducing drug’s intended action
  • Birth: metabolic enzymes may not be fully developed, and in elderly individuals, enzymatic activity tends to decrease, further complicating drug metabolism
640
Q

Where is Drug Excretion (Elimination)?

A

Urine, Faeces, Bile

641
Q

Describe the relationship between drug absorption and elimination

A

Occur simultaneously:

  1. Absorption at the beginning
  2. At the Peak: absorption equals elimination
  3. After the peak: mainly elimination takes place
641
Q

Are polar drug metabolites in Phase II metabolism reabsorbed?

A

NO
- excreted in urine

641
Q

Formula for Drug Clearance?

A

CL = Rate of Drug Clearance / {Drug} Plasma

641
Q

What are First-order Kinetics?

A

When rate of elimination is directly proportional to conc of medication in body

  • VMAX: max rate of drug elimination
  • Km: half of max. rate of elimination
641
Q

How is Drug elimination accomplished?

A

By renal filtration of blood plasma

641
Q

What is Drug Clearance?

A

Volume of plasma cleared of drug per unit time (L/hour or mL/minute)

  • helps determine required dosage rate to maintain desired drug conc in the plasma
  • represents a flow parameter and doesn’t specify amount of drug removed from body
641
Q

What is Elimination Half-life (t½)?

A

Time it takes for plasma conc of medication to decrease by half

  • Useful when designing therapeutic dosing regimen
641
Q

Formula for Elimination Half-life (t½)?

A

t½ = (0.693 x Vd) / CL

641
Q

What is the concept of Steady State in pharmacokinetics?

A

Achieved after approximately 5 half-lives of drug administration

  • when rate of drug administration = rate of elimination (stable conc of drug in plasma)
642
Q

What are Zero-order Kinetics?

A

Rate of elimination is constant

  • elimination mechanisms become saturated, and elimination rate reaches max capacity (VMAX)
  • rate of elimination doesn’t depend on drug’s conc in body
642
Q

What are the determinants of Elimination half-life (t½)?

A
  • Clearance (CL) increases → t½ decreases - caused by Cytochrome P450 induction
  • Clearance (CL) decreases → t½ increases - caused by Cytochrome P450 inhibition, cardiac, hepatic, or renal failure
  • Volume of distribution (Vd) increases → t½ increases - as seen in cases of pathological fluid accumulation or obesity with increased adipose tissue
  • Volume of distribution (Vd) decreases → t½ decreases - related to aging and decreased muscle mass
643
Q

Describe Homeostasis

A

Steady state - closely maintained

  • stress on cells results in attempt at adaptation
643
Q

What is the Dosage rate required to maintain steady state?

A

[Drug]plasma × CL

643
Q

What is Hyperplasia?

A

Increase in cell number due to stimuli

  • Physiological (normal) - eg: breast tissue in puberty, response after loss of tissue

Pathological (hormonal imbalances) - eg: excess oestrogen → endometrial hypoplasia, hyperplasia of lymph nodes in response to infection

  • Reversed upon stimulus withdrawal
643
Q

What is Hypertrophy?

A

Increase in cell size

  • occurs in response to mechanical stress
  • often in non-dividing cells - eg: skeletal muscle
  • can lead to dysfunction (e.g. heart failure)
644
Q

What are Growth Receptors?

A

Stimulate cell division and growth

3 types:

  • Intrinsic tyrosine kinase receptors
  • 7-transmembrane G protein-coupled receptors
  • Receptors without intrinsic tyrosine kinase activity
645
Q

What is Atrophy?

A

Reduction in cell size

  • Physiological (e.g. embryological structures, post-menopausal uterus)

Pathological (e.g. decreased workload, blocked blood supply, loss of innervation)

  • Mechanisms: reduced cellular components, protein degradation
  • Hormones promote degradation (thyroid hormone) or growth (insulin)
645
Q

“p53 doesn’t cause cell cycle arrest between G1 and S phase” TRUE/ FALSE

A

FALSE

645
Q

“Water and most electrolytes are reabsorbed into blood circulation by renal tubes” TRUE/FALSE

A

TRUE

646
Q

What are Telomeres?

A

Caps which protect chromosome ends from degradation and fusion

  • smaller with each division
646
Q

Causes of Infection?

A
  • Foreign bodies
  • Immune reaction
  • Necrosis: STRONG inflammatory response
647
Q

What vascular changes occur in response to injury?

A

Vasodilation - mediated by histamine and nitric oxide - increased blood flow, Calor (warmth), Rubor (redness)

648
Q

What are cellular changes that occur in response to injury?

A
  • Stasis (slowed blood flow due to vasodilation)
  • Margination (WBC accumulation near vessel wall)
  • Rolling (WBCs roll along cell wall)
  • Adhesions (binding of WBCs to vessel wall via selectins and integrins)
  • Transendothelial migration (WBCs move through leaky vascular endothelium. Mediated by histamine, bradykinin, substance and leukotrienes. Pass through junctions - diapedesis, transcytosis)
648
Q

Difference between Diapedesis and Transcytosis

A

D: WBCs squeeze through blood vessel walls to reach infection site

T: cells transport molecules across their interior and release them on other side

649
Q

” Selectins: expressed on endothelial and white cells

Intergrins: bind to ICAM’ TRUE/FALSE

A

TRUE

650
Q

Examples of Intergrins?

A
  • Vascular cell adhesion molecule (VCAM)
  • Intracellular adhesion molecule (ICAM)
650
Q

What is Chemotaxis?

A

Process in which WBCs follow a chemical gradient to move along it, leading them to site of inflam.

  • Cytokines, such as C5a and C3a, are potent chemotactic factors
650
Q

How does vascular permeability change in response to injury?

A

Increases - leaky vessels

  • results in loss of proteins from blood, causing changes in osmotic pressure. Therefore, water follows the proteins out of the vessel, leading to swelling
650
Q

What are the steps of Phagocytosis?

A
  1. Recognition and Attachment
    • involve opsonins, mannose receptors, recognition of bacterial surface glycoproteins and glycolipids containing terminal mannose residues. Opsonins include complement and IgG
  2. Engulfment
    - phagosome is formed as the cell engulfs foreign particle - joins with a lysosome to form phagolysosome
  3. Killing and Degradation
    - achieved through generation of reactive oxygen species by NADPH oxidase and reactive nitrogen species by nitric oxide synthase
650
Q

Clinical features of Inflammation?

A
  • Calor (heat)
  • Dolor (pain)
  • Rubor/Erythema (redness)
  • Tumor (swelling)
651
Q

What mediates dolor (pain)?

A

Prostaglandins, Bradykinin

651
Q

How can you distinguish acute inflammation from other conditions like swelling due to a tumor or cyst?

A

Acute inflammation: characterised by presence of neutrophils

Swelling due to tumor/cyst may lack this inflammatory cell presence

651
Q

How is tumor (swelling) caused by vascular changes?

A

Proteins exit leaky blood vessels, leading to changes in osmotic pressure

651
Q

Outcomes of Inflammation?

A
  • Resolution (healing)
  • Suppuration (pus, formation of abscesses)
  • Chronic inflammation (lymphocytes and macrophages)
  • Restitution (scar tissue)

→ one can lead to another

651
Q

What causes erythema (redness) and calor (heat) in response to injury?

A

E: increased perfusion and slow blood flow

C: increased vessel permeability

651
Q

What does “Functio laesa” refer to in the context of injury?

A

Loss of function

651
Q

What is the main inflammatory cell that characterises acute inflammation, and what are its characteristics?

A

Neutrophils

  • phagocytic and cytotoxic abilities

They are granulocytes

652
Q

What is Resolution in the context of healing, and what are the key processes involved?

A

Complete restoration of tissue to normal after removal of inflammatory components

  • Involves processes such as macrophages clearing necrotic tissue and debris, and reabsorption of lost fluid into tissues and vessels
652
Q

Factors that can affect the process of resolution in healing?

A
  • Severity of infection
  • Duration of infection
  • Location of infection - determined by blood supply innervating area
653
Q

In what medical condition might empyema occur, and why might it not be treated with antibiotics?

A

Empyema can occur in a space filled with pus that is walled off

  • not effectively treated with antibiotics: low blood supply to abscess, which hinders delivery of inflammatory cells for healing
  • Surgical draining needed
653
Q

What characterises Chronic Inflammation?

A

Persistent injury
- last for weeks to months

653
Q

What type of immune cells are typically involved in Chronic inflammation?

A

Lymphocytes and Macrophages

  • Ls produce various cytokines that help maintain inflam. and activate Ms to clear debris
653
Q

How can Mycobacteria be detected in Chronic inflammation?

A

Ziehl-Neelsen (ZN) stain - myco. can’t be digested by Ms

  • Positive ZN stain = presence of mycobacteria
653
Q

What is Suppuration, and what is typically found in pus formed during this process?

A

Formation of pus
- contains neutrophils, bacteria, inflammatory debris

654
Q

What are common causes of Chronic inflammation?

A
  • Persistent infections
  • Autoimmune diseases
  • Hypersensitivity diseases
654
Q
A
654
Q
A
655
Q
A
655
Q
A
656
Q

What is a Granuloma, and how is it formed?

A

Small area of inflam. formed due to chronic inflam

  • consists of aggregated epithelioid cells
656
Q

Granulomas will form in response to?

A
  1. Mycobacteria
  2. Parasites
  3. Foreign bodies
  4. Cancers
656
Q
A
656
Q

Describe the structure of a granuloma

A

Sponge-like centre composed of epithelioid cells and multinucleated cells, surrounded by cuff of Ls

657
Q

What role does a granuloma play in the body?

A

Trap pathogens and form a protective shell around them, preventing further damage

  • T cells play role in formation of granulomas by producing cytokines that activate macrophages to create granulomas
657
Q

What is meant by “Restitution”?

A

Formation of scarring during the repair process in response to tissue injury

657
Q

Are granulomas associated with foreign bodies, and what are examples of these foreign bodies?

A

YES

  • both endogenous and exogenous.
657
Q

Is scarring reversible, and what are the potential consequences of scarring in certain organs?

A

Irreversible

  • In organs like the heart, scarring can lead to loss of muscle tissue after events like MI. Scarring in liver is associated with cirrhosis
657
Q

What is Apoptosis, and when does it typically occur

A

Programmed cell death

  • Eg: occurs during natural replacement of skin cells
657
Q

When is Restitution, most likely to occur during repair process?

A
  • Lots of necrosis (intensity of injury)
  • Lots of fibrin
  • Poor blood supply
  • Length of time injury persists for
658
Q

What are the 2 main categories of cell death?

A

Apoptosis: can be intrinsic or extrinsic

Necrosis (accidental cell death): due to external factors like infection or internal factors like ischemia (reduced blood flow)

659
Q

What is Coagulative Necrosis?

A

Occurs when tissue becomes hypoxic

  • cell not completely destroyed
  • microenviron. too toxic for proteolysis, preventing cells from clearing up debris
  • common: seen in MI
659
Q

What are the differences between necrosis and apoptosis?

A

Necrosis: pathological, affects adjacent groups of cells, causes increase in cell size, passive process, leads to an inflam. reaction

Apoptosis: pathological or physiological, affects single cells, causes decrease in cell size, active process, and doesn’t induce an inflam. reaction

659
Q

What is Caseous Necrosis?

A
  • Occurs when dead cells disintegrate but aren’t fully digested
  • ‘Cheesy’
  • Ask for culture, PCR and look for Ziehl Neelson stain
  • A result of fungal or mycobacterialinfection
    • usually associated with TB
659
Q

What is Liquefactive Necrosis?

A
  • Occurs when hydrolytic enzymes fully digest dead cells, resulting in formation of creamy substance (pus) with no cell structure remaining
  • associated with bacterial and fungal infections, brain injuries
660
Q

Describe the steps in the pathway of Apoptosis

A
  1. Cells undergo shrinkage (Pyknosis)
  2. Chromatins condense, leading to clumping and breaking up of nucleus
  3. Cytoplasmic blebs form, causing cytoplasm to break up
  4. Ms enter to clear away cellular debris
661
Q

What is the Extrinsic pathway for apoptosis?

A

Initiated by death signaling proteins/receptors like TNF and Fas

  • TNF: associated with apoptosis in inflam.

Fas: involved in recognising self, leading to apoptosis, especially in Ls

  • Mutations in Fas contribute to autoimmune diseases
661
Q

Causes of Cellular Aging?

A
  • Oxidative stress from free radical damage (e.g. radiation)
  • Accumulation of metabolic by-products like Lipofuscin
661
Q

How is Apoptosis physiological or pathological?

A
  • Physiological: normal growth, removal of self-reactive Ls, hormonal-dependent involution
  • Pathological: injury, chemo, viral infection
661
Q

What is the Intrinsic pathway for apoptosis?

A

Involves mitochondria becoming leaky

  • Proteins like Bax and Bak cause release of cytochrome C, stimulating caspase activation
662
Q

Impact of Calorie Restriction on lifespan?

A

Extend life by reducing IGF signaling, which can silence specific genes

663
Q

What is p53?

A

Acts as a sensor for DNA damage and can halt cell cycle

  • If DNA damage is irreparable, p53 stimulates caspases and induces apoptosis
664
Q
A
664
Q

“Too little apoptosis can lead to…”

A

Cancers and Autoimmune diseases

664
Q
A
664
Q
A
665
Q

“Excessive apoptosis may contribute to..”

A

Neurodegenerative disorders

665
Q

What are the characteristics of Anabolic processes in metabolism?

A

Endergonic, Reductive
- Reducing Agent: NADPH + H+

665
Q

Describe Catabolic processes in metabolism

A

Exergonic, Oxidative
- Reducing Agent: NADH + H+

665
Q

How is ATP produced through aerobic glycolysis?

A

Oxidation of glucose to pyruvate

  • Efficient process
665
Q

What is the outcome of anaerobic glycolysis in terms of ATP production?

A

Yields lactate

  • Rapid, inefficient process
665
Q

Where and in what forms is glucose stored in the body?

A

Stored as disaccharides
- polyaccharides in liver

666
Q

“Oxidation of glucose through the pentose phosphate pathway yields …..”

A

Ribose-5-phosphate

667
Q

How does glucose enter cells, and what are the transport mechanisms?

A

Via Na+/glucose symporters

  • passive facilitated diffusion through GLUTs (1-5)
667
Q

What is the end product of glycolysis?

A

Converts glucose to 2 pyruvate molecules per glucose, with net gain of 2 ATP

667
Q

What are the first 2 steps of glycolysis?

A
  1. Hexokinase/glucokinase converts glucose to glucose-6-phosphate (irreversible)
  2. Phosphoglucoisomerase converts glucose-6-phosphate to fructose-6-phosphate
668
Q

Which step in glycolysis is both irreversible and rate-limiting?

A

Phosphofructokinase-1 (PFK) phosphorylates fructose-6-phosphate to fructose-1,6-bisphosphate, consuming 2 ATP

669
Q

What enzyme cleaves fructose-1,6-bisphosphate?

A

Aldolase

  • into 2 interconvertible 3C molecules (G3P and another)
669
Q

What is the final step in glycolysis?

A

Pyruvate kinase oxidises a 3C molecule to pyruvate, producing ATP

669
Q

“H+ decreases glycolysis if too much lactic acid produced” TRUE/FALSE

A

TRUE

670
Q

What is produced in the absence of oxygen during anaerobic metabolism?

A

Lactic acid

671
Q

Describe the steps involved in the production of lactic acid during anaerobic metabolism

A
  1. Pyruvate takes H+ ions from NADH
  2. Pyruvate converted into lactate, regenerating NAD
672
Q

What is the Warburg Effect?

A

High-rate anaerobic glycolysis in cancer cells

673
Q

How do cancer cells utilise anaerobic glycolysis?

A

Cancer cells have low Km hexokinase

674
Q

How can cancer be treated by targeting glycolysis?

A

Using enzymes around control points

674
Q

What are the advantages and disadvantages of the Warburg Effect?

A
  • ADVs: rapid energy production, support for cell proliferation
  • DISs: production of H+ and lactate, inefficient ATP synthesis, high glucose consumption leading to weight loss in cancer patients
674
Q

What happens to NAD+ during glycolysis?

A

Glycolysis reduces NAD+ to NADH and H+

  • NADH must be regenerated through oxidative metabolism of pyruvate
674
Q

What are the steps of the TCA cycle?

A
  1. Pyruvate enters mitochondrial matrix
  2. Pyruvate dehydrogenase converts pyruvate to acetyl-CoA
  3. Acetyl-CoA combines with Oxaloacetate (C4) to form Citrate (C6)
  4. C6 decarboxylated twice, yielding 2x CO2
  5. Four oxidation reactions produce 3 NADH, H+, FADH2
  6. 1 GTP formed, converted to ATP
  7. Oxaloacetate (C4) regenerated
675
Q

Where are the enzymes of the TCA cycle located?

A

Matrix except Succinate Dehydrogenase - integrated into inner mitochondrial membrane

676
Q

Products of TCA cycle?

A
  • 4 ATP, 10 NADH, 6 CO2, 2 FADH2
  • 3 pairs of electrons transferred in conversion of NAD+ to NADH and H+
  • 1 pair of electrons needed to reduce FAD to FADH2
677
Q

What conditions suggest a lack of energy in the cell?

A

High ADP and NAD+

677
Q

What factors indicate high energy in the cell?

A

High ATP, NADH, acetyl-CoA

677
Q

“High succinyl-CoA and acetyl-CoA indicate lots of precursor molecules for biosynthetic reactions” TRUE/FALSE

A

TRUE

678
Q

What is the conversion that occurs in oxidative phosphorylation, and what is the source of the phosphoryl transfer potential for ATP?

A

Electron transfer potential of NADH+ and FADH2 is converted into the phosphoryl transfer potential of ATP

679
Q

What does the phosphoryl transfer potential refer to?

A

Change in free energy (ΔG) during ATP hydrolysis

679
Q

How is the electron transfer potential of a compound measured?

A

Measured by the redox potential of a compound (E’0), indicating how easily it donates electrons

680
Q

What does a Negative redox potential (E’0) indicate?

A

Reduced form of the compound has a lower affinity for electrons than hydrogen

680
Q

How is ATP produced in oxidative phosphorylation?

A

By donating electrons to complexes in membrane

680
Q

What are the entry points for electrons in the electron transport chain?

A

Enter from NADH through the malate-aspartate shuffle and from FADH2 through glycerol-3-phosphate

680
Q

What is the role of Cytochromes in the electron transport chain, and what happens in the respiratory chain?

A

Proteins with heme groups

  • In resp chain, electrons are transferred from carriers with positive potentials to oxygen, resulting in conversion of oxygen to water
680
Q

Which respiratory complexes pump H+ ions?

A

Complexes 1, 3, 4 pump H+ ions into the intermembrane space of mitochondria, creating proton gradient

680
Q

How is ATP synthesised in oxidative phosphorylation, and what is the ATP yield from 1 NADH and 1 FADH2?

A
  • ATP is synthesised as H+ flows back into matrix through ATP synthase
  • 1 NADH yields 3 ATP, 1 FADH2 yields 2 ATP
681
Q

How do cyanide, azide, CO affect oxidative phosphorylation?

A

Inhibit transfer of electrons to O2, preventing formation of proton gradient and synthesis of ATP

681
Q

How many ATP molecules are produced from one molecule of glucose through glycolysis, TCA cycle, and oxidative phosphorylation?

A

30-32 ATP molecules

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MEDICINE YEAR 1 (4 decks)

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