membrane structure and function I

Question 1

What does phosphatidylcholine do? [3 marks]

Answer 1

• Maintains structural integrity of the cell
• Involved in cell signalling
• Involved in enzyme activation

Question 2

What does phosphatidylserine do? [1 mark]

Answer 2

Involved in apoptosis (signals to macrophages)

Question 3

What does phosphatidylethanolamine do? [2 marks]

Answer 3

• Plays a part in membrane fusion

- Involved in disassembly of the contractile ring during cytokinesis

Question 4

What does phosphatidylinositol do? [3 marks]

Answer 4

• Linked to a lipid (e.g. glycerophosphatidylinositol)
• Involved in cell signalling
• Plays a role in membrane trafficking

Question 5

Cholesterol structure [3 marks]

Answer 5

• Large and flat
• Mostly hydrophibic
• Has polar -OH group

Question 6

What are glycolipids important for? [2 marks]

Answer 6

• Cell recognition

- Membrane stability

Question 7

Which phospholipids are usually found on the inner leaflet of the membrane? [2 marks]

Answer 7

• Sphingomyelin

- Phosphatidylserine

Question 8

Which phospholipids are usually found on the outer leaflet of the membrane? [3 marks]

Answer 8

• Phosphatidylserine
• Phosphatidylethanolamine
• Phosphatidylinositol

Question 9

How does temperature affect the fluidity of the membrane? [2 marks]

Answer 9

• High temperature: decreased fluidity

- Low temperature: increased fluidity

Question 10

How does the composition of fatty acid affect fluidity of the membrane? [2 marks]

Answer 10

• Saturated fatty acids: more compact = low fluidity

- Mixture of fatty acids: less compact = high fluidity

Question 11

How does chain length affect fluidity of the membrane? [2 marks]

Answer 11

• Short: less viscosity = more fluidity

- Long: more viscosity = less fluidity

Question 12

Why do longer fatty acid tails affect fluidity of the membrane? [1 mark]

Answer 12

Higher chance of forming more intermolecular interactions

Question 13

How does cholesterol content affect fluidity of the membrane? [1 mark]

Answer 13

Higher content = less fluidity

Question 14

What does the ATP dependent flippase do when synthesising membranes? [1 mark]

Answer 14

Moves phospholipids from the outer to the inner leaflet

Question 15

What does the ATP dependent floppase do when synthesising membranes? [1 mark]

Answer 15

Moves phospholipids from the inner to the outer leaflet

Question 16

What does scramblase do when synthesising membranes? [1 mark]

Answer 16

Moves phospholipids in both directions

Question 17

Structure of integral proteins [3 marks]

Answer 17

• Single OR multi pass
• Strong non-covalent bonds
• Trans-membrane domain (usually alpha helix)

Question 18

What is a single pass in the context of membranes? [1 mark]

Answer 18

Where the molecule crosses through the membrane once (via integral proteins)

Question 19

What is a multi pass in the context of membranes? [1 mark]

Answer 19

Where the molecule crosses through the membrane multiple times (via integral proteins)

Question 20

What do integral proteins interact with? [1 mark]

Answer 20

Phospholipid bilayer

Question 21

Peripheral proteins structure [2 marks]

Answer 21

• Either on extra-cellular or cytosolic membrane

- Weakly associated by non-covalent bonds

Question 22

What do peripheral proteins interact with? [2 marks]

Answer 22

• Integral proteins

- Lipid polar head groups

Question 23

What are lipid anchored membrane proteins? [1 mark]

Answer 23

Proteins that are covlanetly linked to a lipid (e.g. glycerophosphatidylinositol)

Question 24

What is one example of a function for lipid anchored membrane proteins? [1 mark]

Answer 24

Blood groups

Question 25

What are carbohydrates associated with in membranes? [2 mark]

Answer 25

• Membrane lipids

- Proteins

Question 26

What are membrane carbohydrates involved in? [2 marks]

Answer 26

• Cell-cell interactions

- Cellular recognition