Membranes & Receptors

Question 1

What are the 5 general functions of biological membranes?

Answer 1

• Highly selective permeable barrier
• Control of enclosed chemical environment
• Communication
• Recognition of signalling molecules
• Signal generation in response to stimuli

Question 2

What % of a hydrated membrane is water?

Answer 2

20%

Question 3

What are membranes comprised of? And in what proportions?

Dehydrated

Answer 3

• 40% Lipid
• 60% Protein
• 1-10% Carbohydrate

Question 4

What characteristic of phospholipids allows them to form structures in water?

Answer 4

Amphipathic

Question 5

What 2 structures can phospholipids form in water?

Answer 5

Micelles and Bilayers

Question 6

What do phospholipids consist of?

Answer 6

• Glycerol
• 2 Fatty Acids
• Phosphate head group

Question 7

What is unique about Sphingomyelin?

Answer 7

Only phospholipid not based on glycerol

Question 8

What is the difference between Cerebrosides and Gangliosides?

Answer 8

Cerebrosides contain sugar monomers whereas Gangliosides contain oligosaccharide sugars

Question 9

What is an unsaturated phospholipid?

Answer 9

One in the Cis conformation where double bonds form between fatty acids creating a kink

Question 10

What effect do unsaturated phospholipids have on membrane fluidity?

Answer 10

Increased Fluidity

Question 11

What are the 4 modes of phospholipid mobility in the bilayer?

Answer 11

• Flexion
• Rotation
• Lateral Diffusion
• Flip Flop

Question 12

What is the effect on membrane fluidity due to cholesterol at high temperatures?

Answer 12

Reduced fluidity due to formation of hydrogen bonds

Question 13

What are membrane proteins required for?

Answer 13

• Facilitated Diffusion
• Ion Gradient
• Specificity Of Cell Response

Question 14

What proof is there of membrane proteins?

Answer 14

• Membrane Fractionation and SDS PAGE Electrophoresis

- Freeze Fracture

Question 15

What are the 2 types of membrane protein and what is the main difference between them?

Answer 15

• Peripheral are on the surface

- Integral are deeply embedded

Question 16

Why is orientation of membrane proteins important?

Answer 16

• For function as the recognition site must be on the correct side of the membrane

Question 17

Name the 3 modes of motion for membrane proteins

Answer 17

• Conformational Change
• Rotation
• Lateral

Question 18

Name 3 things that restrict membrane protein mobility

Answer 18

• Lipid mediated effects
• Membrane protein associations
• Extramembranous protein association

Question 19

Name the 2 components of the cytoskeleton

Answer 19

• Spectrin

- Actin

Question 20

What does an antiparallel Spectrin heterodimer consist of?

Answer 20

-An alpha and beta Spectrin rod wound together

Question 21

What is the function of adapter proteins in the cytoskeleton?

Answer 21

• Attach the Spectrin-Actin network to the membrane proteins

Question 22

What is Hereditary Spherocytosis and what is the consequence?

Answer 22

• Spectrin depletes by 40-50%
• Erythrocytes round up
• Prone to lysis
• Haemolytic Anaemia

Question 23

What is the function of the stop transfer sequence?

Answer 23

• Causes the ribosome to detach

- Spans the bilayer forming transmembranous region