Membrane Bi-layer Flashcards

(41 cards)

0
Q

What is the composition of the membrane?

A

40% lipid
60% protein
1-10% carbohydrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

Give some of the functions of the biological membrane

A
  • Continuous, highly selective permeability barrier
  • Allows control of the enclosed chemical environment
  • Communication
  • Recognition of signalling molecules, immune surveillance and adhesion proteins
  • Signal generation in response to stimuli (electrical or chemical)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does it mean if a molecule is amphipathic?

A

It has hydrophilic and hydrophobic regions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How are phospholipids named?

A

Phosphatidyl-X

Where ‘x’ is whatever the head group is

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What type of bond introduces a kink in the fatty acid chain of the phospholipid?

A

A cis bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How is a glycolipids formed?

A

When a phosphocholine moiety is replaced with a sugar on a phospholipid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the difference between cerebrosides and gangliosides?

A

They are both types of glycolipid
Cerebroside - head group is a sugar monomer
Ganglioside - head group is an oligosaccharide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How is the lipid bilayer formed?

A

It is spontaneous in water

Driven by Van der Walls attractive forced between hydrophobic tails

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What forces is the bilayer stabilised by?

A

Electrostatic and hydrogen bonding between hydrophilic moieties
Interactions between hydrophilic groups and water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What percentage does cholesterol make up of the total membrane lipid?

A

45%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the structure of cholesterol?

A

A polar head group
A rigid, planar steroid ring structure
A non-polar, hydrocarbon tail

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What effects does cholesterol have on the bilayer?

A

It reduces phospholipid packing, increasing fluidity

It reduces phospholipid chain motion, reducing fluidity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What could form a head group in a phospholipid?

A

Choline, amine, amino acid, sugars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What movements can phospholipids do?

A

Lateral diffusion
Flexion
Rotation
Flip flop

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What effect do cis double bonds have on the bilayer?

A

Reduce packing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What functional evidence is there for proteins in the bilayer?

A

They carry out facilitated diffusion, produce ion gradients and there is specificity to cell responses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What biochemical evidence is there for proteins in the membrane?

A

Freeze fracture

Membrane fractionation and gel electrophoresis

17
Q

What movements can proteins carry out?

A

Conformational change
Rotation
Lateral diffusion

18
Q

What movement can proteins NOT carry out?

19
Q

How is membrane protein mobility restricted by other proteins?

A

Aggregates with other proteins

Tethered to basement membrane or internal structures eg cytoskeleton

20
Q

What are the lipid mediated effects in protein mobility restriction?

A

Most proteins tend to go to cholesterol-poor regions in the membrane

21
Q

How do peripheral membrane proteins associate with the bilayer?

A

Electrostatic and hydrogen bond interactions

22
Q

How can peripheral proteins be removed from the bilayer?

23
Q

How do integral membrane proteins interact with the bilayer?

A

Interact with hydrophobic regions

24
How are integral proteins removed?
Need detergents or organic solvents that compete for the non-polar interactions in the bilayer
25
Give an example of when asymmetrical protein orientation is important
Receptor for a hydrophilic extracellular molecule such as insulin needs to have its recognition site facing towards the extracellular space for it to function.
26
Give the structure of spectrin
α and β subunits wind together to form an anti-parallel heterodimer. Two heterodimers form a head-to-head association to form a heterotetramer of α2β2.
27
Give properties of spectrin
Long and floppy
28
Describe how actin and spectrin are in the cytoskeleton
Rods of spectrin are cross-linked by short, actin profilaments. Band 4.1 and adducin molecules form interactions towards the ends of the spectrin rods.
29
How is the actin-spectrin network attached to the membrane?
Through adapter proteins: Ankyrin (band 4.9) Band 4.1
30
Why is the erythrocyte cytoskeleton important?
Allows erythrocytes to pass through very narrow capillaries without lysis.
31
How does dominant hereditary spherocytosis lead to haemolytic anaemia?
Spectrin levels are depleted by 40-50%. Cells are more round and become less resistance to lysis. Cleared by the spleen so shortened life Bone marrow is unable to compensate enough for shortened life span -> haemolytic anaemia.
32
What type of backbone are phospholipids based on?
Glycerol
33
Which carbon atoms of glycerol are fatty acid side chains attached to?
C1 and C2
34
Where are phospholipids synthesised?
In the ER
35
What are two common carbon chain lengthens in the fatty acid side chains of phospholipids?
C16 and C18
36
Which bonds can peripheral membrane proteins form with the membrane?
Electrostatic interactions Hydrogen bonds Disulphide bonds
37
Name some peripheral membrane proteins of the erythrocyte cytoskeleton
``` Spectrin Actin Adducin Band 4.1 Ankyrin ```
38
Name two integral membrane proteins of the erythrocyte skeleton
Band 3 - anion exchanger | Glycophorin A
39
What length are membrane spanning domains of membrane proteins normally?
Between 18 and 22
40
Which secondary structure are membrane spanning domains normally?
Alpha-helix