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week 2 Flashcards

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1
Q

Lipid bilayer

A

Dynamic and selectively permeable
Contains membrane proteins enables signalling, communication and selective permeability

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2
Q

What do membrane proteins do

A

Signalling, communication and selective permeability

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3
Q

What do the fatty acids chains in membrane determine

A

Fluidity of membrane

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4
Q

What does amphipathic mean

A

Both hydrophobic and hydrophilic
Phospholipids are amphipathic

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5
Q

Intracellular signal transduction lipids

A

Rapidly generated/ destroyed by enzymes in response to a specific signal
Spatially and temporally generated - highly specific signal
Bind specifically to conserved regions found within many different proteins and once bound induce conformational and/or localisation and activity changes within these proteins

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6
Q

How does cholesterol alter properties of lipid bilayers

A

Cholesterol inserts between membrane phospholipids
This tightens packing in the bilayer/ membrane rigidity and decreases membrane permeability to small molecules

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7
Q

what does the fluidity of membranes allow

A

Signalling lipids and membrane proteins to rapidly diffuse in the lateral plane and interact with one another
Ensures membranes are equally shared between daughter cells following cell division
Allows membranes to fuse with other membranes e.g. exocytosis

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8
Q

Integral and peripheral membrane proteins

A

Single pass- integral
Multi pass transmembrane protein- integral : hydrophobic amino acids with side chains interacting with lipid mono layer
B-barrel- integral
Lipid-linked -peripheral
Peripheral membrane protein -peripheral

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9
Q

What are functions of membrane proteins

A

Transport
Enzymatic activity
Signal transduction
Cell-cell recognition
Intercellular joining- connecting neighbouring epithelial cells
Attachment to cytoskeleton and extracellular matrix ECM

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10
Q

Types of passive transport

A

Simple diffusion: no membrane proteins involved, driven by concentration gradients
Facilitated diffusion- membrane proteins involved, driven by concentration gradients
No energy input ATP required for either

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11
Q

What does the ability of a solute to cross membrane by simple diffusion depend on

A

Concentration gradient
Hydrophobicity/ charge
Size
Membranes highly impermeable to ions- hydrophobic molecules can pass through

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12
Q

What are the two classes of facilitated diffusion

A

Channels- discriminates mainly on size and charge
Uniporter carrier proteins- involves a binding site for solutes, highly specific, binding of molecule to specific site causes conformational change resulting in movement of molecule from inside to outside
Transport inorganic ions/ small molecules across the membrane passively along their concentration/electrochemical gradient

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13
Q

What are channel proteins

A

Membrane proteins that form hydrophilic pores through plasma membrane
Most are non-directional ion channels
Show some selectivity based on size and charge
Fast
Gated channels offer more control than a simple membrane pore

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14
Q

What’s an electrochemical gradient

A

Combines the concentration gradient and membrane potential
The force driving a charged solute across a membrane is the concentration gradient and membrane potential

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15
Q

Why do cells maintain electrochemical gradients

A

To drive transport across membranes
To maintain osmotic balance
Electrical forces must be balanced
Without active transport to maintain electrochemical gradients ions would flow down their gradients through leak channels disturbing osmotic balance which results in cell death

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16
Q

How do cells carry out active transport

A

ATP driven pumps (primary active transport)- couple the transport of a solute against its gradient to the hydrolysis of ATP
Coupled transporters (secondary active transport)- couple the transport of one solute with the gradient to another against gradient
Light driven pumps found in plants and bacteria not humans -couple the transport of a solute against its gradient to the input of energy from light

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17
Q

How do coupled transporters work

A

Move solutes against concentration/ electrochemical gradient by coupling transport to Na+ gradient created by Na+/K+ ATPase
Do not depend directly on the hydrolysis of ATP (secondary active transport)
Symport- same directions
Antiport- opposite directions
Couple the transport of one solute with the gradient to another against gradient

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18
Q

Cell cycle

A

G1 and G2 are gap phases between mitosis and DNA synthesis
In G1 cells monitor their intracellular and extracellular environment to determine if conditions are correct during interphase cells continue with transcription and grow in mass

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19
Q

What is the restriction point in cell cycle

A

During G1
Decides whether to go into the cell cycle
G0 normal state for most cells (quiescence) not going through cell cycle
No growth factors

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20
Q

G1/S checkpoint

A

Will stop cell cycle if DNA is damaged

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21
Q

What do cyclin dependent kinases Cdks do

A

Regulate cell cycle checkpoint transitions
Are themselves regulated by feedback
Activating molecules are cyclins, proteins that cyclically fluctuate in concentration in cell cycle

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22
Q

What is a kinase

A

An enzyme which activates/ deactivates a protein by phosphorylating them

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23
Q

How do different cyclin-Cdk complexes regulate entry into different phases of cell cycle

A

Cyclins accumulate during the G1 S and G2 phases of cell cycle
By the G2 checkpoint enough cyclin is available to form M-Cdk (maturation promoting factor) complexes which initiate mitosis
Later in mitosis M-Cdk switches itself off by initiating a process which leads to destruction of cyclin
Cdk persists in cell as inactive until it associates with new cyclin synthesised during interphase

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24
Q

Consequences of checkpoint failure

A

Proliferation of cells in absence of growth factors
Replication of damaged DNA
Segregation of incompletely replicated chromosomes
Division of cells with wrong number of chromosomes

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25
What is metabolism
The chemical processes that occur within a living organism in order to maintain life
26
What do catabolic pathways do
Break down complex molecules into simple molecules and release energy
27
What do anabolic pathways do
Build complex molecules from simple molecules and require energy usually in form of ATP
28
Oxidation
Loss of electrons
29
Reduction
Gain of electrons
30
Functions of connective tissue
Structural support for body and organs Tensile strength Binding tissues together Immune defence Metabolism and energy storage Cushioning Elasticity
31
What’s a fibroblast cell
Main cell type in non-specialised connective tissue Produce and maintain extracellular matrix ECM and ground substance Spindle shaped cell Cigar shaped nucleus Activated myofibroblasts involved in wound healing >> fibrosis
32
Fixed connective tissue cells
Fibroblasts Fibrocytes- inactive fibroblasts Adipocytes- fat cells Macrophages- phagocytic immune function derived from monocytes
33
Wandering connective tissue cells
Plasma cells- oval nucleus actively produces antibodies Eosinophils- 2 lobe nuclei eosinophilic granules Neutrophils- multilobed nuclei phagocytic functions Lymphocytes- round nuclei with small cytoplasm Mast cells- basophilic granules inflammatory reactions histamine production
34
What is ground substance
Transparent semi solid gel Part of extracellular matrix Amorphous Fibres are embedded in ground substance Glycosaminoglycan GAGs backbone, GAG often is hyaluronic acid Contains glycoproteins and complex carbohydrates Hydrophilic binds water Makes it strong resists compressive forces Provides volume to connective tissue
35
What are elastin fibres
Secreted as precursor tropoelastin polymerises to become elastin requires glycoprotein fibrillin scaffold Found in skin, ears, arteries, lung, bladder Allows stretch and recoil to maintain shape
36
What are collagen fibres
Main fibre type, high tensile strength, flexible but can break, formation is triple alpha helix, thicker than elastin, doesn’t branch
37
Types of collagen fibres
Type 1- bone, skin, tendons, ligaments Type 2 - cartilage Type 3- reticular fibres reticulin Type 4- basement membrane
38
What are reticular fibres
Delicate and thin Form the framework of organs/ glands and blood vessels
39
How do we classify different types of connective tissue
Density of tissue- loose vs dense Arrangement of fibres- regular vs irregular
40
What is lamina propria
Loose connective tissue Immediately underlying certain epithelia Very thin CT layer Ground substance and loosely arranged fibres Allows blood vessels to serve epithelial tissues above Good for diffusion Good breeding ground for microbes Usually has immune cells
41
What’s the difference between dense irregular connective tissue and dense regular connective tissue
Irregular connective tissue the fibres are randomly arranged so are strong and can withstand pressure from different directions Regular connective tissue fibres are organised in parallel good tensile strength but only resists forces in one direction
42
what is adipose tissue
Also known as fat tissue, its a connective tissue that’s mainly composed of fat cells called adipocytes There’s two types of adipose tissue - white and brown
43
White adipose tissue
Unilocular Have a single large lipid droplet Look empty in sections Can stain with Oil red O/Sudan Red Most common in adult Main function is to store excess energy in the form of fatty molecules mainly triglycerides Other functions are to insulate body, cushion vital organs, secrete hormones and biological factors
44
Brown adipose tissue
Multilocular Have many smaller lipid droplets Look empty in sections- lipid washed away Most common in newborn In adult found around kidney/adrenals Rich in mitochondria Rich in capillaries Specialised for thermogenesis
45
What are adipocytes
Energy storing cells that contain large globules of fat known as lipid droplets surrounded by a structural network of fibres
46
What are some genetic mutations in connective tissue
Type 1 collagen- osteogenesis imperfecta - brittle bones/malformation Type 2 collagen- chondrodysplasia- cartilage defects, joint abnormalities Type 1, 3 or 5 collagen- Ehlers Danlos syndrome- fragile, extra elastic skin, hypermobility joints Fibrillin- Marfan’s syndrome - affects tissues rich in elastic fibres- aorta skeletal defects- long digits and arms
47
What does pluripotent mean
Potential to become any cell type
48
Multipotent
Can be lots but not every cell type
49
What does unipotent
Specialised, only one cell type
50
What is oligopotent
Can make a few cell types
51
What are hematopoietic stem cells
HSCs give rise to all blood cells types via committed oligopotent progenitor cell intermediates
52
DNA binding domain
Binds to the DNA sequence
53
Activation domain
Interacts with RNA polymerase
54
What is connective tissue made up of
Fibres Ground substance Cells The fibres and ground substance make up the extra cellular matrix
55
Connective tissue definition
Composed of cells and a significant amount of extra cellular matrix. Differ in their physical properties because of differences in the types of cells and the composition of the extracellular matrix. There are different classes of connective tissue Provides structural and metabolic support for other tissues and organs
56
Ground substance definition
The ground substance is a viscous, clear substance and is highly hydrated It’s composed of proteoglycans-highly hydrophilic molecules that trap water within the matrix Fibres are embedded in an amorphous ground substance which is the component of connective tissue that occupies the space between the fibres and the cells
57
Loose connective tissue definition
One of the two subclasses of connective tissue One of its roles is to support epithelial tissue Works to hold organs in place and is made up of extracellular matrix and collagenous elastic and reticular fibres
58
Dense connective tissue definition
What makes up tendons and ligaments and consists of a higher density of collagen fibres Contains fewer cells and less ground substance in comparison with loose connective tissue
59
Ehlers-Danlos syndrome
EDS is a heterogeneous group of connective tissue disorders. They are characterised by joint hyper mobility, skin hyperextensibility , and tissue fragility It can result from mutations in genes for the structure and synthesis of collagen. There are many subtypes
60
Marfan syndrome
A disorder of the body’s connective tissues, a group of tissues that maintain the structure of the body and support internal organs and other tissues Heritable, autosomal dominant, mutation in the gene for fibrillin Characteristics: being tall, abnormally long and slender limbs, deformity of chest wall, fingers and toes (arachnodactyly), heart defects, lens dislocation Gene defect leads to abnormal production of fibrillin resulting in parts of body being able to stretch abnormally when under stress No cure. Genetic tests used for diagnosis
61
Function of glycolipids and glycoproteins
Glycolipids- allow recognition by other cells e.g. cells of the immune system Glycoproteins- allow cell communication (cell signalling)
62
4 major phospholipids in the mammalian plasma membrane
Phosphatidylethanolamine Phosphatidylserine Phosphatidylcholine Sphingomyelin All have similar structure so are able to link together (only head group is different except for sphingomyelin) Other 3 all have central glycerol molecule
63
Intracellular signal transduction lipids
Phosphatidylinositol Diacylglycerol Ceramide Sphingosine-1-phosphate Minor proportion of the (phospho)lipid content of intracellular membranes. Derived from lipids residing in the plasma membrane Rapidly generated/ destroyed (to prevent continuous signals) by enzymes in response to a specific signal Spatially and temporally ( at a specific space at a specific time) generated= highly specific signal Bind specifically to conserved regions found within many different proteins and once bound, induce conformational and/or localisation and activity change within that protein in membrane helping to increase signal (drive increased transduction)
64
Uniporter carrier proteins
Glucose transporter Glut2 in gut epithelia Highly selective- transported molecule bound to carrier Relatively slow
65
ATP driven pumps
Move solutes against concentration/electrochemical gradient by expending energy E.g Na+ K+ ATPase Operates continuously to expel Na+ that enters cell through other carrier proteins and channels. Hydrolyses ATP to ADP both an enzyme and carrier protein, couples the export of Na+ to import of K+ 1) 3 Na+ bind inside cell, pump hydrolyses ATP and is phosphorylated 2) Na+ dependent phosphorylation causes pump to undergo conformational change, Na+ transferred across membrane and released 3) 2 K+ bind outside cell and pump is dephosphorylated 4) K+ dependent dephosphorylation causes pump to return to its original conformation. K+ is transferred across membrane and released
66
Na+/ glucose symporter (gut epithelia)
Na+ electrochemical gradient used to drive movement of glucose against its gradient [Na+] high in gut low in cell. [glucose] high in cell low in gut Binding of Na+ and glucose is cooperative i.e.binding of glucose is dependent on Na+ Because [Na+] is much higher outside cell glucose is more likely to bind to symporter when its in initial state- allows for binding of extracellular molecules As a result there’s an overall net flow of glucose against its concentration gradient and Na+ along concentration gradient into cell
67
Na+/Ca2+ antiporter
Important in cardiac muscle Cardiac muscle cell contraction is triggered by a rise in intracellular [Ca2+] Much higher concentration of Na+ and Ca2+ outside cell than inside Therefore antiporter moves 3Na+ in cell along gradient for every 1 Ca2+ out against gradient Antiporter rapidly reduces intracellular Ca2+ concentration which reduces strength of cardiac muscle contraction i.e. causes cardiac muscle relaxation
68
Main function of the cell cycle
Growth and development

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