1.1 The Membrane Bilayer

Question 0

Describe the general composition of the dry weight of the membrane bilayer

Answer 0

40% lipid
60% protein
1-10% carbohydrate

Question 1

List the functions of the membrane bilayer (5)

Answer 1

Continuous, highly selective permeability barrier
Control of the enclosed environment
Communication
Recognition
Signal generation

Question 2

What % of the total membrane weight is water?

Answer 2

20%

Question 3

What are phospholipids made up of?

Answer 3

Fatty acids
Glycerol
Phosphate
Head group

Question 4

Define ‘amphipathic’

Answer 4

Both hydrophilic and hydrophobic

Question 5

Give examples of species that can act as head groups in a phospholipid (4)

Answer 5

Choline
Amines
Amino acids
Sugars

Question 6

What length of carbon chain is most prevalent in a phospholipid?

Answer 6

16-18

Question 7

How does sphingomyelin differ from a normal phospholipid?

Answer 7

Sphingomyelin does not use glycerol

Question 8

Describe a glycolipid

Answer 8

No phosphate joining group

Sugar containing lipids

Question 9

Define a ‘cerebroside’

Answer 9

A phospholipid with a sugar monomer as the head group

Question 10

Define a ‘ganglioside’

Answer 10

A phospholipid with an oligosaccharide as the head group

Question 11

Describe a lipid micelle

Answer 11

A ring of phospholipids with the hydrophilic heads facing outwards and the hydrophobic heads facing inwards

Question 12

Describe a lipid bilayer structure

Answer 12

2 layers of phospholipids. The hydrophobic tails face each other and the hydrophilic heads face outwards

Question 13

Describe the movement of ‘flexion’

Answer 13

Side to side movement

Question 14

Describe the movement of ‘rotation’

Answer 14

Stationary movement in a circle

Question 15

Describe the movement of ‘lateral diffusion’

Answer 15

Phospholipids move along the chain laterally

Question 16

Describe the movement of ‘flip-flop’

Answer 16

Moves from the inner layer to the outer layer

Question 17

Explain the function of a cis double bond in a phospholipid carbon chain. Where do the unsaturated chains come from?

Answer 17

Double bonds cause the chains to kink. This results in the chains being more spaced out which reduces phospholipid packing. The unsaturated chains are required from the diet.

Question 18

Describe the structure of cholesterol

Answer 18

Cholesterol has a rigid planar steroid ring structure with a polar head group. It also has a more flexible non-polar hydrocarbon chain.

Question 19

How does cholesterol affect the fluidity of the bilayer

Answer 19

Reduces: rigid structure causes reduced chain motion
Increases: reduces phospholipid packing