Peerwise Flashcards
(232 cards)
1
Q
Define the term genome.
A
- Hint - dictionary*
- The genome contains all of the genetic information of the organism.
- first level of information in every cell
- what COULD happen
2
Q
Define the term transcriptome.
A
- Hint - the selected words*
- All of the mRNA molecules that can be expressed from the genes of an organism.
- starts to give cells their own identity
- what MIGHT be happening
3
Q
Define the term proteome.
A
- Hint - completed novel*
- the actual proteins that are translated from the mRNA of that cell
- what DOES happen
4
Q
How are proteins produced from RNA?
A
- DNA transcribed into mRNA so the information can leave the nucleus
- mRNA moves to a ribosome
- ribosome made up of rRNA
- mRNA ‘read’ at the ribosome
- tRNA carries amino acids to ribosome for assembly
- tRNA has anticodons which ‘match’ with mRNA codons so it knows which amino acid to bring
5
Q
What are the 3 stages of protein assembly?
A
- Initiation - start codon (AUG), translation begins, first amino acid brought
- Elongation - more and more amino acids being added to polypeptide chain
- Termination - stop codon, chain is complete
6
Q
What can happen at the smooth ER?
A
- lipid synthesis
- metabolism
7
Q
What happens at the rER?
A
- protein secretion
8
Q
Where are soluble intra-cellular proteins synthesised?
A
At free ribosomes in the cytoplasm
9
Q
How does the genetic code give rise to different amino acids and polypeptide chains?
A
- there are 4 bases (A, T, G, C)
- 1 codon is made up of 3 bases and will code for 1 amino acid
- 3^4 = 64 combinations but only 20 amino acids
- amino acids are coded for by the triplet of bases
- the mRNA sequence will contain a series of triplets/codons which is basically the series of amino acids that are needed to form a specific polypeptide
10
Q
At what end of the DNA strand would we start to read?
A
5’
11
Q
What does degeneracy in the code help to protect against?
A
MUTATION
- when amino acids can be coded for by more than one triplet of bases then this protects against mutation
- if one triplet is mutated, another may not be and so appropriate amino acid may still be produced
12
Q
What is the basic structure of an amino acid?
A
- A central carbon atom
- a single H
- a carboxyl group (COOH)
- an amino group (NH2)
- an R group (the variable part which gives the amino acid it’s specific properties)
13
Q
List the amino acid families.
A
- small (small R group)
- hydrophobic
- aromatic (benzene ring)
- nucleophilic
- amide (ONH2)
- basic (+ve charge)
- acidic (-ve charge)
14
Q
What is conservative amino acid substitution?
A
Similar amino acids have similar codons > if a mutation occurs a similar amino acid may be coded for and the impact on the polypeptide may not be as great.
15
Q
How do amino acids join together to form a polypeptide?
A
They form peptide bonds via a condensation reaction.
16
Q
List some examples of post-translational modifications.
A
- acetylation
- sumolyation
- lipidation
- hydroxylation
- glycosylation
- disulphide bond
- ubiquitination
- methylation
- phosphorylation
17
Q
Briefly describe glycosylation.
A
- addition of a large sugar chain
- helps proteins to interact with other ‘partner’ proteins
- increases half life of protein due to size/complexity of sugar chain
- can affect orientation e.g. keep membranous protein in fixed position rather than moving around
18
Q
Briefly describe phosphorylation.
A
- addition of a phosphate group
- alters activity of the protein
- many receptors use phosphorylation to transmit a signal through a cell
- involved in intracellular communication
- important in enzyme function
- controlled by enzymes (kinases add, phosphatases remove)
19
Q
How can more than 20 proteins be made from only 20 amino acids?
A
- post translational modifications
- proteolytic cleavage
20
Q
What is a zymogen?
A
An inactive pro-enzyme
21
Q
What is proteolytic cleavage?
A
The breakdown of proteins into smaller polypeptides or amino acids
22
Q
Give an example of proteolytic cleavage.
A
Chymotrypsinogen is cleaved by proteolytic enzymes to form chymotrypsin.
23
Q
What is the primary structure of a protein?
A
The sequence of amino acids.
24
Q
What is the secondary structure of a protein?
A
The amino acids start to fold in to structures e.g. a-helices or b-sheets
25
What is the tertiary structure of a protein?
The proper folding of a protein into its final shape
26
What is the quarternary protein structure?
An overall protein made up of more than 1 protein coming together.
27
Discuss mutations in sickle cell anaemia and the effects of the mutation.
- an inherited disease which causes problems with oxygen transport around the body
- caused by a mutation in the B-glob in gene which encodes for the B sub unit of haemoglobin
- the mutation changes only 1 codon out of 146 codons
- GAG mutates to GTG at the 6th codon which changes glutamic acid to valine
- this changes the shape of haemoglobin which changes RBC from biconcave disc to sickle shaped
28
How are proteins used therapeutically?
- recombinant = man made, gene isolated and grown in bacteria to create artificial therapeutics e.g. insulin, growth factors
- antibodies = essential in vaccinations
- peptide memetics = multiplied protein that biologically mimics action of protein
- blockers of protein function
29
What is the purpose of the cell cycle?
To produce 2 daughter cells (replication).
30
What is quiescence?
- also known as G0
- the phase when cells are not actively dividing
- not always a permanent phase, cells may be in G0 and then re-enter the cell cycle
- response to external signal/mitogenic factor
- erythrocytes are permanently in G0
31
What are the stages of the cell cycle?
G1
S phase
G2
M phase
32
What phases make up the interphase of the cell cycle?
G1, S, G2
33
What happens during the M phase?
- mitosis
| - cytokinesis
34
What happens during G1?
- takes about 11 hours
- the cell grows in size (having just been replicated through mitosis it will be half size)
- monitoring the external environment to wait for the optimal conditions for cell division
- monitoring for growth factors
- RNA and protein synthesis in preparation for S phase
- are conditions favourable for proliferation?
35
Define the cell cycle.
The interval between 2 successive mitotic divisions resulting in the production of 2 daughter cells.
36
What happens during G2?
- takes about 4 hours
- preparing for cell division
- further growth
- duplication of cell organelles
- was chromosome replication formed correctly?
37
What happens during S phase of the cell cycle?
- takes about 8 hours
| - DNA synthesis occurs
38
What is cytokinesis?
The cleavage of a cell to produce daughter cells.
39
What are the phases of mitosis?
* Hint - PPMAT*
- Prophase
- Pro-metaphase
- Metaphase
- Anaphase
- Telophase
40
What happens during prophase of mitosis?
- chromatin condensation
- nucleolus disappears
- centrioles move to poles
41
What happens during pro-metaphase in mitosis?
- nuclear membrane dissolves
| - chromosomes attach to microtubules and start moving
42
What happens during metaphase of mitosis?
- spindle fibres align the chromosomes along the middle of the cell nucleus (metaphase plate)
43
What happens during anaphase of mitosis?
- paired chromosomes separate and move to opposite sides of the cell
44
What happens during telophase of mitosis?
- chromatids arrive at opposite poles of cell
- new membranes form around the daughter nuclei
- chromosomes decondense
- spindle fibres disperse
45
When does mitosis start and stop in relation to the cell cycle?
Start - after G2
| Stop - before G1
46
What are the key molecules in regulating progression through the cell cycle?
Cyclin dependent kinases (CDKs)
47
What type of kinase are CDKs?
Serine/threonine - this means that they phosphorylate proteins with serine/threonine in them.
48
What CDKs are important in moving from G1 - S phase?
CDK4/6
49
Which CDK is important in moving from G1 through S phase?
CDK2
50
List CDKs in the order in which they are important during the cell cycle
CDK4/6 (G1- start S)
CDK2 (end G1 - end S)
CDK2 (mid S - metaphase)
CDK1 (end G2 - M)
51
How is CDK activity regulated?
- cyclins
- phosphorylation/dephosphorylation
- CKIs
52
Discuss cyclins
- small, short lived proteins
- must be associated with a CDK to be active
- unstable proteins
- up or down regulated depending on phase of the cell cycle
53
List the CDK and cyclins association of the cell cycle.
- CDK4/6 - cyclin D
- CDK2 - cyclin E (end G1 - end S)
- CDK2 - cyclin A (mid S - M)
- CDK1 - cyclin B
54
What is CDK1-cyclin B also known as?
Maturation promoting factor (MPF)
55
How do cyclins actually regulate CDKs?
- the presence/absence of a cyclin determines whether or not a CDK will be active
56
What are CKIs?
Cyclin-dependent kinase inhibitors
- small proteins that block cyclin/CDK activity
- block either by forming an inactive complex or acting as a competitive CDK ligand
57
What are the 3 families of CKIs?
- p21 CIP
- p27 KIP
- p16 INK
58
How does MPF go from inactive to active?
- CDK1 is phosphorylated
- cyclin b levels start to rise G2
- they then bind to CDK1
CDK1 is dephosphorylated and active
59
What does a kinase do?
Phosphorylation
60
How does CDK1-cyclin B contribute to mitosis?
Phosphorylates lamins:
- results in disassembly of intermediate filaments of the lamina, so lamina is destroyed
Phosphorylates condensins and his tones:
- results in chromosome condensation
Phosphorylates microtubule associated proteins (MAPs)
- allows for spindle formation
61
What are checkpoints in the cell cycle and what do they do?
A type of cell monitoring:
- checking for favourable external environment (growth factors)
- checking for favourable internal environment (sufficient growth)
- checking for DNA damage/replication errors
- checking the integrity of the mitotic spindle and chromosome attachment
- checking the chromosome integrity
62
Why are checkpoints needed?
To ensure that 2 viable daughter cells are produced with perfectly replicated and segregated chromosomes.
63
What are the 4 checkpoints of the cell cycle?
1. Restriction checkpoint
2. DNA damage checkpoint (late G1)
3. DNA damage checkpoint (late G2)
4. Metaphase checkpoint
64
Discuss the restriction checkpoint.
- checks for sufficient growth factors
- the point after which the cell does not need any more growth factors and commits to cell division
- dependent on the accumulation of cyclin D
- happens 2-3 hours before S phase begins
- retinoblastoma (RB) protein is the gatekeeper
65
What are growth factors?
Secreted signalling molecules that act on cells, affecting their growth, behaviour and rate of proliferation.
- affect through influencing cell differentiation
66
List some growth factors involving in the cells of the skin and what they do.
Epidermal Growth Factor - re-epithelialisation - keratinocytes proliferation and migration
Platelet Derived Growth Factor - matrix formation - increased numbers and activity of fibroblasts AND remodelling (production of proteases)
Vascular Endothelial Growth Factor - angiogenesis - endothelial cell proliferation and migration
67
How does RB work as the gatekeeper at the restriction point?
- it inhibits E2F
- E2F is a transcription factor which is needed to transcribe the genes for S phase
- SO the cell cycle cannot move to S phase while RB is inhibiting E2F
68
How does the restriction checkpoint work?
- RB inhibits E2F
- growth factors activate cyclin D
- cyclin D activates CDK4/6
- CDK4/6 Phosphorylates RB
- phosphorylated RB no longer binds to E2F
- E2F can transcribe genes for S phase
69
What is a tumour suppressor gene (TSG)?
A gene that can encode normal proteins to inhibit cell proliferation in order to ensure that the cell can maintain the integrity of its genome and only divide when necessary. TSGs will arrest the cell until appropriate conditions are met and repair DNA damage.
70
List some examples of TSGs?
Retinoblastoma (RB) - blocks entry to cell cycle
P53 - detects DNA damage
BRCA1 - DNA in breast cancer
71
How do the DNA damage checkpoints work?
- check for damage e.g. chemical mutagens, radiation, replication errors
- TSG p53 detects DNA damage
- this results in production of p21 (a CKI)
- at late G1 checkpoint, p21 will bind to CDK2-cyclin E/A to halt progression to S phase
- at late G2 checkpoint, p21 will bind to CDK1-cyclin A/B to halt progression to M phase
72
Discuss the TSG p53
- a transcription factor
- directly transcribes genes to halt the cell cycle
- if p53 senses low levels of p21/DNA damage then it will arrest the cell to repair damage
- if p53 senses high level of p21/DNA damage it will induce apoptosis
73
How does the metaphase checkpoint work?
- while chromosomes are unattached the checkpoint remains ‘on’ meaning mitosis cannot proceed to anaphase
- once all chromosomes are attached the inhibition is removed and the anaphase promoting complex in activated which allows for the separation of sister chromatids to opposite poles of the cell
74
List the major organelles/sub-cellular structures of a typical human cell.
- plasma membrane
- nucleus
- ribosomes
- mitochondria
- endoplasmic reticulum
- rough endoplasmic reticulum
- Golgi apparatus
- cytoskeleton
- lysosomes
- peroxisomes
- endosomes
75
Describe the structure of the plasma membrane of a typical human cell.
- phospholipid bilayer
- proteins dotted throughout (transmembranous and peripheral)
- cholesterol molecules
- carbohydrates
- amphipathic
- semi-permeable
- fluid mosaic model
76
What are the functions of the plasma membrane of a typical human cell?
- regulate entry and exit from the cell
- cell signalling
- support (attachment to ECM or cytoskeleton)
- site for enzyme activity
- form membrane for sub-cellular organelles
77
How does the plasma membrane interact with the extracellular environment?
Through integral plasma membrane proteins:
- allow transfer of small molecules across the membrane
- through pumps, carriers, channels
Through plasma membrane receptors:
- interact with a specific ligand
- initiate a cascade of chemical signals in the cell
78
Discuss the composition and function of the nucleus.
- bound by a double membrane ‘nuclear envelope’
- DNA packaged as chromatin
- nuclear pores facilitate entry and exit to nucleus
- membrane supported by nuclear lamina
- nucleolus synthesises rRNA and ribosomes
Function:
- DNA replication (mRNA), gene expression (transcription/post-transcriptional modification)
79
Why is it important that the cell compartmentalises into different organelles?
- to provide a permissive environment for a set of biochemical functions
- to protect the cell by segregating destructive enzymes and chemicals
- to localise cellular processes for efficient functioning
- to separate molecules required for specific functions
80
Describe the structure of mitochondria.
Outer membrane:
- contains portions (proteins which allow movement of ions into and out of the mitochondrion)
- also enzymes involved in elongation of fatty acids and oxidation of adrenaline
Inner membrane:
- folded into Cristal to increase SA available for ATP production
- contains enzyme ATP synthase which generates ATP in matrix
- contains transport proteins that regulate movement of metabolites into and out of matrix
Inter membrane space between outer/inner membrane (NOT same as matrix)
Matrix:
- space within the inner membrane
- contains enzymes of Krebs and fatty acid cycles
- contains DNA, RNA, ribosomes and calcium granules
81
Discuss the function of the mitochondria.
- ATP production
- store capsases which are responsible for triggering apoptosis (cytochrome C)
- transiently store calcium to contribute to calcium homeostasis
- abundant in ovum for development, possibly in sperm for motility
82
Describe the structure and function of the endoplasmic reticulum.
```
Structure:
- continuous with nuclear membrane
- system of flattened sacs (cistern are)
Function:
- synthesis
```
83
Describe the structure and function of rough endoplasmic reticulum.
Structure:
- ribosomes attached to cytoplasmic surface
Function:
- takes developing proteins from cytosol and continues their development
- post-translational modifications
- proteins destined for ECM (mucous and enzymes)
- proteins associated with the cell membrane (receptors and channels)
- proteins for membrane bound vesicles (enzymes of lysosomes)
- protein folding
- abundant in plasma cells for production of immunoglobulins
84
Describe the structure and function of smooth endoplasmic reticulum.
Structure:
- does not contain ribosomes
- usually less extensive than rER except in some specialised tissues
- contains cytochrome P450 enzymes which are important in the metabolism of certain drugs and toxins
Function:
- synthesis of lipids, phospholipids and steroid
- calcium storage
- abundant in hepatocytes for lipid synthesis and Leydig cells for steroid hormone biosynthesis
85
What is the difference between rER and sER?
- RER has ribosomes attached, sER does not.
- rER plays role in synthesis and folding of proteins
- sER synthesises lipids, phospholipids and steroids
86
Describe the role, structure and function of the Golgi apparatus.
Structure:
- 5-8 folds called cisternae
- cisternae network faces the nucleus, forms a connection with ER and is entry point to Golgi
- cis/medial/trans-golgi are the major processing areas that allow biochemical modifications
- trans-golgi network is the exit point for vesicles budding off the Golgi surface (packaging and sorting)
Function:
- modifies proteins and lipids that it receives from ER
- abundant in plasma cells due immunoglobulin production
87
What is the address label for proteins bound for the lysosome?
Mannose-6-phosphate
88
What are lysosomes?
- vesicles containing hydrolytic enzymes
- have a low pH
- degrade defective/old organelles, macromolecules, particles taken in from outside cell
89
What are endosomes?
* HINT - ‘endo’ meaning in*
| - vesicles involved in transport of molecules from plasma membrane to lysosome
90
What are peroxisomes?
- a compartment for enzymes involved in oxidative reactions
| - also involved in biosynthesis of bile acids, fatty acid metabolism and detoxification
91
Discuss Tay-Sach’s disease
- build of lipid in neuronal bodies and processes
- because of failure to degrade lipids
- causes neurological regression, seizures and blindness
- rare and usually fatal
- genetic
92
What are the functions of the cytoskeleton?
- to organise cell structure, maintain the correct shape of the cell
- support fragile plasma membrane
- provide mechanical linkages to allow cell/tissue to bear stress
- allows cell to adopt specific behaviours (e.g. growth, division, migration, motility)
93
What types of filament are found in the cytoskeleton?
```
Microtubules:
- composed of tubulin monomers
Microfilaments:
- composed of actin
Intermediate filaments:
- can be made up of keratin, vimentin, desmin and lamins
```
94
What are the motor proteins for microtubules and microfilaments?
Microfilaments/actin - powered by myosin
Microtubules - powered by dynein/kinesin
95
What forms the basis of cell projections? Give examples.
Actin Microfilaments
E.g. microvilli which increase SA for absorption in the gut
E.g. stereocilia that detect sound in the inner ear
96
What filaments form a cortical network in the cytoplasm? What does it facilitate?
- Actin
- cell contraction
- shape change
97
What filaments help to produce membrane extensions such as lamellipodia and filopodia?
- actin
| - helps with cell motility
98
What role do actin filaments play in cytokinesis?
Contractile ring formed at the cleavage furrow to separate dividing cells.
99
Where are intermediate filaments likely to be found?
In cells that require strength e.g. epithelial cells
- keratin in keratinocytes of epidermis
- vimentin in fibroblasts of the dermis
- lamins in the nuclear lamina
100
Discuss microtubules
Structure:
-highly dynamic
- cylindrical tubes
- continually grow and shrink thus push and pull associated structures
- organising centre is the centrosome which initiates microtubule growth towards periphery
Functions:
- mitotic/meiotic chromosomal movement
- intracellular vesicle/organelle transport
- ciliary and flagellar motility
101
Describe the movements of kinesins and dyneins
Kinesins move cargo away from the centrosome
| Dyneins move cargo towards the centrosome
102
What is an axoneme?
A structure composed of microtubules and dynein that allows for bending (role in movement)
103
Where are cilia found?
In the respiratory tract where they help to move mucous, and entrapped dust and microbes, away from the lungs. Also found in the Fallopian tubes where they assist the movement of the ovum towards the uterus.
104
What type of cell uses a flagella for propulsion?
Sperm cells.
105
Discuss Kartagener’s syndrome.
- associated with defects in cilia and flagella
- due to mutations in dynein protein
- can cause recurrent respiratory infections as cilia cannot sweep mucous away from lungs
- can cause infertility in males as sperm are immotile
106
What type of filaments are found in the mitotic spindle?
Microtubules
107
What are cellular junctions?
- transmembrane protein complexes
- connect the plasma membrane to adjacent cells, basement membrane and cytoskeleton
- three types: anchoring, occluding/tight, communication/GAP
108
Discuss the function and types of anchoring junctions.
```
Function:
- provide mechanical stability to groups of epithelial cells so they can function cooperatively
Types:
- adherens
-desmosomes
- focal adhesions
- hemidesmosomes
```
109
What junctions do the actin filaments of cytoskeleton interact with?
- adherens (cell - cell)
| - focal adhesions (cell - ECM)
110
What junctions do intermediate filaments interact with?
- Desmosomes (cell - cell)
| - hemidesmosomes (cell - ECM)
111
Discuss epidermolysis bullosa simplex.
- occurs due to defective intermediate filaments (hemidesmosomes)
- disrupts dermal-epidermal layer to result in severe blistering
112
Discuss the structure and functions of tight junctions
Function:
1. Create a seal to prevent diffusion of molecules between adjacent cells
2. Create a barrier within epithelial cell membranes to prevent mixing of membrane proteins, creating apical and basolateral membranes.
e.g. blood-brain barrier, blood-retinal barrier
Structure:
- cell-cell contact
- connects to actin cytoskeleton
113
Discuss the structure and function of GAP junctions.
Structure:
- cell-cell contact
- composed of hexameters of connexins
Functions:
- present in most cells
- intercellular channels which connect the cytoplasms of adjacent cells
- permit passage of inorganic ions and other small molecules
- found in large numbers during embryogenesis
- also important in cardiac and smooth muscle where they pass signals involved in contraction
114
What conditions can arise from a mutation in connexin-26?
- inherited human deafness
- Vohwinkel syndrome (disorder of the skin resulting in thick, honeycomb like callouses and a build up of abnormal fibrous tissue)
115
Discuss the importance of cell junctions in the skin.
Adherens junctions: hold epithelial cells together
Desmosomes: provides strength for epidermal keratinocytes (integrity of epidermis)
Tight junctions: provide a seal in stratum granulosum, prevent fluid from passing across an epithelial sheet
Hemidesmosomes: hold dermis to epidermis at dermo-epidermal junction
Gap junctions: allow for passage of small molecules between cells
116
What type of immune cell has an extensive rER and why?
Plasma cells, because they produce immunoglobulins (antibodies) which are made up of proteins.
117
Describe the structure and function of free ribosomes.
Structure:
- made from rRNA
Function:
- mostly produce proteins for use within the cell
118
List some consequences of defective organelles/structures within a cell.
Mitochondria - mitochondrial cytopathies (defects in oxidative phosphorylation)
Lysosomes - Tay-Sach’s disease
Microtubules - Kartagener’s syndrome
Gap junctions - Cx26 mutation causes deafness and Vohwinkel syndrome
Hemidesmosomes (intermediate filaments) - epidermolysis bullosa simplex
119
What are stem cells?
Unspecialised cells that can self renew indefinitely and can differentiate into specialised cells.
120
What is differentiation?
The process in which relatively unspecialised cells acquire specialised structural or functional traits.
121
What is a progenitor cell?
A descendent of a stem cell with a limited ability to self renew, proliferate and give rise to specialised cells i.e. a precursor to a fully differentiated cell.
E.g. in haematopoiesis
122
What is the hierarchy of stem cells?
Totipotent
Pluripotent
Multi potent
Unipotent
123
What is a totipotent stem cell?
A cell that can give rise to embryonic membrane and any cell type of the adult body
E.g. the zygote
124
What is a pluripotent stem cell?
A cell that can give rise to any cell type of the adult body.
E.g. embryonic stem cell.
125
What is a multipotent stem cell?
A cell that can give rise to tissue specific cell types of the adult body.
E.g. haematopoietic, neural, mesenchymal
126
What is a unipotent stem cell?
A cell that can give rise to only one specific type of cell.
E.g. germ line stem cell, epidermal stem cell
127
Where do human embryonic stem cells (hESC) originate from and how are they sourced for research?
- they are derived from the inner cell mass of the blastocyst
- in the UK, hESCs come from embryos that were originally created for IVF
- if an embryo has been unsuited for or unused in IVF then the donors can donate it for research
- use of hESCs is highly regulated
128
What are adult/somatic stem cells? Can they be used in research?
- undifferentiated cells found throughout the body that replenish and regenerate dying/damaged cells
- e.g. mesenchymal and haematopoietic
- they can be obtained from a tissue sample but they are difficult to isolate as they are few in number
- it is difficult to keep them proliferating in culture
129
What are induced pluripotent stem cells and why would they be useful in research?
- they are cells that are treated with transcription factors in order to switch on genes to induce and maintain pluripotency
- they would be useful as would reduce the need for embryonic stem cells (ethical issues around embryonic stem cells)
130
What are cancer stem cells?
- these exhibit characteristics of both stem cells and cancer cells
- they are defined by the ability to generate more stem cells (self renewal) and to produce cells that differentiate
- as well as self renewal and differentiation abilities, CSCs have the ability to see tumours when transplanted into an animal host
131
What is CSC-targeted therapy trying to do?
* Hint - nip it in the bud*
- to kill the tumour stem cell
- if this could be killed it would mean that the tumour not be able to make new cells and continue growing and will eventually degenerate
132
What is regenerative medicine?
- methods to regrow, repair or replace damaged or diseased cells, organs or tissues
- includes the generation and use of therapeutic stem cells, tissue engineering and production of artificial organs
133
List some of the potential therapeutic used for stem cells.
- regenerative medicine
- tissue repair
- drug screening
- vehicles for gene therapy
134
What is an example of stem cell therapy?
- bone marrow transplants used to treat blood disorders such as leukaemia
- patient would receive a course of injections to stimulate release of stem cels into their blood (peripheral blood stem cell)
135
What does the term ‘autologous’ mean?
(Of cells or tissues) obtained from the same individual.
136
What does allogenic mean?
Taken from a different individual of the same species.
137
What is Holoclar?
- a tissue engineered product
- used to restore sight in the absence of deep corneal stroma damage
- an undamaged area of the eye is biopsied to isolate limb all stem cells
- stem cells are then grown in a lab using cell culture techniques
- a sheet of cornea is produced that can be transplanted onto the eye
138
What is the corneal stroma?
- has a pivotal role in normal visual function
| - made up of dense, regularly packed collagen fibrils arranged in orthogonal layers
139
Can cartilage be created for transplants, in vitro?
- stem cells can be differentiated into chrondocytes in vitro
- however, cartilage which is regenerated by stem cells fails to fully recapitulate the structural and bio mechanical properties of the original cartilage
140
List some of the medical application of stem cells.
- cartilage transplants
| - make new blood
141
What is cell potency?
A cell’s ability to differentiate into other cell types. The more cell types that a cell can differentiate into the greater the potency.
142
A ribosome is composed of 2 units, 40S and 60S, that together amount to 80S. What does the S measure?
The sedimentation rate i.e. how quickly it will settle at the bottom after centrifugation. This is a non-linear measurements dependent on mass, density and shape.
143
Why is the ribosome one of the main antibiotic targets of a bacterial cell?
* Hint - what do ribosomes make*
- target decoding site on small ribosomal subunit (30S) to prevent tRNA binding or moving through ribosome e.g. doxycycline or streptomycin
- target peptide-transferase centre on large subunit (50S) to prevent polypeptide chain elongation e.g. erythromycin
144
What are the 3 mechanisms by which a protein can enter an organelle?
1. Through nuclear pores (selective gates for nuclear proteins found on nuclear envelope)
2. Protein translocators (for proteins moving from cytosol into ER, mitochondria, peroxisomes)
3. Transport vesicles (for proteins moving from the ER onwards)
145
How do ribosomes know to go to the ER?
* Hint - lead the way*
- protein has a signal peptide/sequence
- signal peptide/sequence is guided to ER membrane by a signal recognition particle (SRP) and SRP receptor
- SRP is in the cytosol and binds to the ER signal peptide when its exposed on the ribosome
- SRP receptor is embedded on ER membrane
146
What is the signal peptide?
A specific sequence on the N-terminal of amino acids
147
What happens once the ribosome has arrived at the ER?
- polypeptide threaded through the translocon (protein channel) in the ER
- continues to be created
- signal peptide is cleaved off by signal peptidase (an ER enzyme)
- protein in the ER lumen is encapsulated into a transport vesicle that ‘buds off’ and is secreted from the ER
- heads for Golgi apparatus
148
Use the ‘snail mail’ analogy to describe how a ribosome is led to the ER
- The new protein is the letter which needs to be delivered
- The signal peptide is the address label
- The SRP is the postman
- The SRP receptor in ER membrane is the name plate on the door
- The translocon is the letterbox
149
What is the cis maturation model?
Proteins move through the Golgi stack and undergo enzymatic modification as they do, which labels them from a specific cell destination.
150
How do proteins labelled with mannose-6-phosphate get from the Golgi to the lysosome?
- Mannose-6-phosphate is the address label for the lysosome
- proteins with M6P label will bind to a specific receptor in the Golgi membrane
- they then go to an endosome which will mature to become the lysosome
- e.g. hydrolase
151
Name a post translational modification that takes place in the Golgi apparatus.
Glycosylation e.g. addition of M6P
152
What type of post translational modification is the hall mark of severe neurodegenerative disorders?
Hyperphosphorylation of the protein Tau
153
What is added during acetylation and why?
An acetyl group and in histones this regulates gene expression.
154
What is added during farnesylation and why?
A farnesyl group and to target proteins to the cytoplasmic face of the plasma membrane.
155
What is added during ubiquitination and why?
A ubiquitin chain and to target a protein for degradation.
156
Where will a ribosome take a protein if it does not have a signal peptide?
To the cytosol
157
How do newly synthesised proteins get to the nucleus?
- via a nuclear localisation signal (NLS)
- entry and exit is controlled by the nuclear pore complexes
- small molecules can enter without regulation
- larger macromolecules e.g. RNA and proteins require association with importing to enter and exportins to exit
158
How do proteins destined for the mitochondrial matrix find their way to the mitochondria?
- have a matrix targeting/import sequence on N-terminal
- kept unfolded in order to move through the membrane
- unfolded by binding to ATP-dependent chaperone proteins
- imported through translocases (TIM and TOM)
159
How do proteins destined for peroxisomes know where to go?
- they have a C-terminal tripeptide
160
Why do we need protein degradation?
To get rid of…
- proteins past their ‘sell by’ date
- faulty proteins
- proteins that are foreign to the cell e.g. from pathogens
161
Name two mechanisms for protein degradation
1. Lysosomal
| 2. Proteosomal
162
Discuss lysosomal degradation.
- destruction by lysosomes
- a lysosome is a vesicle which contains destructive enzymes within it
- lysosomal enzymes include lipases, nucleuses, proteases/proteolytic enzymes
- activated by an acidic environment (4.8 pH) inside lysosome
- used for proteins with a long half life (>20 hours) aka autophagy
- used for membrane proteins brought into cell via endocytosis
- used for extracellular proteins brought into cell via receptor-mediated endocytosis
- used for pathogenic proteins brought into cell via phagocytosis
163
What is a proteasome?
- A cylindrical protein complex
- walls formed from protease enzymes with active sites on the inside so they do not degrade wrong proteins
- protein ‘stoppers’ at either end - only open for appropriate proteins
- ATP-dependent
164
What is proteasomal degradation and when is it used?
- proteins degraded by the proteasome
- proteins degrade inside proteasome to produce peptides
- peptides are extruded and digested by cytosolic peptidases
- they are then back to AA and can be recycled
- used for proteins that need to be removed quickly i.e. those with a short half life (seconds or minutes):
- these proteins have a specific PEST sequence (proline, glutamic acid, serine and threonine)
- used for key metabolic enzymes and defective enzymes
- used on proteins tagged with ubiquitin
165
What is the role of ubiquitin in proteasomal degradation?
- proteins to be degraded are ‘tagged’ with ubiquitin in 3 steps:
1. Activation - ubiquitin activated by E1 using ATP, link created between ubiquitin and E1
2. Conjugation - ubiquitin transferred from E1 to E2
3. Ligation - E3 creates a bond between target protein and ubiquitin
- tagged proteins are then recognised, unfolded and translocated
166
What is cell signalling and what does it do?
- cell communication
| - correct signalling allows normal function
167
List some of the things that a cell will ‘sense’
- nutritional status (e.g. glucose, amino acids)
- oxygen supply
- temperature
- pathogens
- other cells:
- hormones
- growth factors
- pro-apoptotic factors
168
List some of the ways in which a cell may ‘respond’
- die
- grow
- divide
- differentiate
- migrate
- change shape
- >< activity
- produce new proteins
- transcribe new genes
- release hormones
169
Why is cell signalling important in medicine?
- coordinates development: e.g. signals called morphogens diffuse to target cells, so closer cells get high concentration, further cells get lower concentration and response of target cell depends on concentration of morphogens that it senses (cells go to correct places)
- homeostasis: e.g. blood glucose levels, cells in pancreas sense high or low levels and initiate an appropriate response (release insulin/release glucagon)
- abnormal signalling causes diseases: e.g. diabetes - not enough of insulin (signalling molecule) to control blood sugar; e.g. cancer mutated K-Ras is too active and causes cells to grow/divide/survive in the absence of growth signal
- many drugs work by targeting signalling proteins
170
What is cyclopia?
- 2 halves of brain have not divided properly from midline so end up with merged eye
- caused by problem in sonic hedgehog signalling pathway during development
171
Give examples of drugs that work by targeting signalling molecules.
- Herceptin/trastuzumabis used in the treatment of breast cancer and targets the cell surface growth factor receptor (HER2)
- Salbutamol is an asthma reliever that targets the cell surface receptor b2
- Gleevec (imatibib) is used in the treatment of chronic myeloid leukaemia and targets the intracellular protein tyrosine kinase (Bcr-Abl)
- Avastin/ bevacizumab is used in the treatment of various cancers and targets VEGF which can help a tumour acquire its own blood supply
172
What types of signals can occur in cell signalling?
- physical (temperature)
- electrical (nerve cells)
- (bio)chemical (hormones, growth factors, neurotransmitters)
173
How can biochemical signals be classified?
- by their chemical structure
| - by their range of action (distance)
174
Use hormones as an example to show how biochemical signals can be classified according to their chemical structure.
1. Amino acid derivatives:
- modified amino acids e.g. adrenaline
- peptide hormones e.g. oxytocin
- protein hormones e.g. insulin, growth hormone
2. Steroid hormones:
- derived from cholesterol e.g. testosterone, cortisol
3. Eicosanoids:
- derived from lipids e.g. prostaglandins
175
How can biochemical cell signals be classified according to their range of action?
- long distance e.g. endocrine via blood
- nearby cells by diffusion e.g. paracrine
- neighbouring cell via cell-cell contact e.g. juxtacrine
- same cell e.g. autocrine
176
What are the 3 stages of signal transduction?
1. Detect
2. Transduce
3. Respond
177
What happens during the detection stage of signal transduction?
The signal or stimulus is detected by a receptor (intracellular or cell surface)
178
What happens during the transduction stage of signal transduction?
The signal is transduced from the site of detection to the part of the cell that will response.
179
What happens during the responsive stage of signal transduction?
Cellular responses are activated. The response will be coordinated with responses to other signals and with responses of other cells.
180
When would an intracellular receptor be used?
- for hydrophobic/lipophilic signalling molecules
- hydrophobic molecules can diffuse through the plasma membrane of target cell and enter directly into the cytoplasm
- e.g. steroid hormones like oestrogen
- e.g. nitric oxide (gas)
181
What role does an intracellular receptor have in signal transduction?
- intracellular receptor binds to signal once it has diffused through membrane
- e.g. in steroid hormones like oestrogen and testosterone
- hormone will bind to receptor protein
- hormone-receptor complex is formed
- hormone-receptor complex acts as a transcription factor
- hormone receptor complex binds to DNA and alter gene expression
182
When would a cell surface receptor be used?
- used for hydrophilic molecules which cannot diffuse through plasma membrane by themselves
- e.g. insulin, adrenaline
183
What role does a cell surface receptor have in signal transduction?
- signal/ligand binds to receptor protein
- cell surface receptor becomes activated when ligand is bound to it
- this results in a conformational shape change of protein
- shape change alters the activity which then leads to a cellular response
184
What are the 3 main types of cell surface receptors?
1. Ion channel linked e.g. glutamate neurotransmitter
2. G-protein linked (GPCR) e.g. adrenaline, serotonin
3. Enzyme linked, key subtype is receptor tyrosine kinases, e.g. growth factors
185
How do ion channel linked receptors work?
- receptor itself or protein adjacent to it is an ion channel
- when signal molecule binds to receptor the channel opens
- ions can flow into or out of the cell, along their concentration gradient
- common in nerve impulse transmission
186
How do GPCRs work?
- signal molecule binds to receptor and this activates a G protein
- G protein activates an enzyme that then transmits the signal into the cell
187
How do enzyme linked receptors work?
- e.g. growth factors
- many growth factors are dimeric
- growth factor binds to 2 halves of receptor
- this brings the receptor together and activates enzyme activity
- this then transmits the signal inside the cell
188
Use EGF as an example to show how a receptor tyrosine kinase (RTK) is used.
- dimeric EGF binds to the receptor
- 2 halves of receptor brought together and activated
- tyrosine kinase domain activated
- autophosphorylation
- this provides docking sites for relay proteins
- relay proteins recruited and transmit signal further into the cell
189
List some benefits of the long chain fatty acids present in breast milk.
1. Essential for brain development
2. Absorption of fat soluble vitamins e.g. vitamin A
3. Major calorie source
190
What type of molecule stimulates haematopoietic stem cells to proliferate and differentiate?
Colony stimulating factors (CSFs)
191
Which area contains Brunner’s glands?
Duodenum of small intestine
192
Which antibody, along with mast cells, is involved in type I hypersensitivity?
IgE
193
What is cranial nerve V and what does it do?
The trigeminal nerve, provides motor for mastication/chewing and sensory for the face.
194
What stain is typically used in the assessment of cervical screening samples?
Papanicolaou (PAP smear)
195
List the attachments of the tongue to the skeleton.
1. Styloglossus attaches to the styloid process
2. Hyoglossus attaches to the hyoid
3. Genioglossus attaches to the mandible
196
How many pairs of spinal nerves are there?
31
197
Which three adult brain structures arise from the rhombencephalon?
1. The pons
2. Cerebellum
3. Medulla oblongata
198
What is spatial summation?
The summation of inputs from DIFFERENT areas of the cell that lead to an action potential.
199
What is temporal summation?
The depolarisation of a neuron due to repeated inputs from the SAME area.
200
What is the sphincter of Oddi and what is its function?
Smooth muscle that surrounds the end portion of the common bile duct and pancreatic duct. It relaxes during a meal to allow bile and pancreatic juice to flow into the intestine.
201
Which cranial nerves are assessed in the brain stem death test?
All except I, XI, XII
202
Describe the Manchester triage system.
Category 1 - red - immediate resuscitation
Category 2 - orange - very urgent (10-15 minutes)
Category 3 - yellow - urgent (60 minutes)
Category 4 - green - standard
Category 5 - blue - non urgent
203
List the actions of latissimus dorsi.
Adducts, extends and medially rotates the upper limb.
204
What percentage of total blood volume is contained within capillaries?
5%
205
Describe Gibb’s reflective learning cycle.
1. Description
2. Feelings
3. Evaluation
4. Analysis
5. Conclusion
6. Action plan
206
What stain is used for counter staining gram negative bacteria?
Safranin
207
Which muscles does the axillary nerve innervate?
Teres minor and deltoid
208
Which muscles does the musculocutaneous nerve innervate?
Brachialis, biceps brachii and Coracobrachialis
209
Which muscles does the median nerve innervate?
Most of the flexor muscles of the forearm, the thenar muscles, the two lateral lumbricals associated with the index and middle fingers.
210
Which muscles does the radial nerve innervate?
Triceps brachii and muscles in the posterior compartment of the forearm.
211
What is the vital capacity of the lungs?
The volume of air that can be maximally exhaled from a maximal inspiration.
212
Which drug targets the final common pathway in the clotting cascade to stop clotting?
Heparin
213
Which type of ion channel will open in response to tension in the membrane?
Mechanically gated ion channels
214
Which signalling molecule is involved in matrix formation and remodelling?
Platelet derived growth factor (PDGF)
215
During pregnancy, which hormone released by the corpus luteum will increase flexibility of the pubic symphysis, increase the flexibility of the ligaments of the sacroiliac/sacrococcygeal joints and help to dilate the cervix during labour?
Relaxin
216
Which organs are found within the umbilical region? (5)
1. Stomach
2. Head of pancreas
3. Duodenum
4. Transverse colon
5. Aspects of both kidneys
217
What structures for the apex of the axilla?
1. Lateral border of first rib
2. Superior border of scapula
3. Posterior border of the clavicle
218
Which structure forms the lateral wall of the axilla?
Intertubercular groove of the humerus
219
Which structures form the medial wall of the axilla?
1. Serratus anterior
| 2. Thoracic wall
220
Which structures form the anterior wall of the axilla?
1. Pectoralis major
2. Pectoralis minor
3. Subclavius muscles
221
Which structures form the posterior wall of the axilla?
1. Subscapularis
2. Teres major
3. Latissimus dorsi
222
What is the auscultation site for the aortic valve?
Right edge of sternum, between 2nd and 3rd ribs
223
What molecules are found in the hydrophobic lipid core on micelles?
1. Insoluble long chain fatty acids
2. 2-monoacylglycerol
3. Tocopherol
4. Carotenoids
224
List the molecules found in the epithelial basement membranes.
1. Collagen IV
2. Perlecan
3. Nidogen
4. Laminin
225
Which molecule mediates the development of smooth muscle?
Serum response factor
226
List the quadriceps muscles of the upper leg.
1. Vastus lateralis
2. Vastus intermedius
3. Vastus medialis
4. Rectus femoris
227
What is the mechanism of action of quinolone antibiotics?
Inhibition of DNA synthesis
228
List the transversospinalis muscles.
1. Semispinalis
2. Multifidus
3. Rotatores
229
Which clotting factor is affected in Von Willebrand’s disease?
VIII
230
What can be given to reverse the effects of Heparin?
Protamine
231
Where would you find a1-adrenergic receptors and what is their function?
Vascular smooth muscle - cause vasoconstriction
232
What are the two phases of the TCA cycle?
1. Decarboxylating (citrate to succinyl CoA)
| 2. Reductive (succinyl CoA to oxaloacetate)
