Cell membrane

Question 1

Lipid molecules make up how much of the membrane?

Answer 1

50%

Question 2

All lipid molecules are __________- that is they have a ___________ end and a ___________end

Answer 2

All lipid molecules are **amphiphilic **- that is they have a hydrophillic end and a hydrophobic end

Question 3

What are the most abundant membrane lipids?

Answer 3

Phospholipids

Question 4

What are the main phospholipids in animal cell membranes?

Answer 4

Phosphoglycerides

Question 5

In addition to phospholipids, the lipid bilayers in many cell membranes contain what?

Answer 5

Cholesterol and glycolipids

Question 6

What are the three components of cholesterol?

Answer 6

A polar head group, a rigid steroid ring structure, and a nonpolar hydrocarbon tail

Question 7

The shape and _________ nature of the phospholipid molecules cause them to form ___________ spontaneously in ___________ environments.

Answer 7

The shape and **amphiphilic **nature of the phospholipid molecules cause them to form **bilayers **spontaneously in **aqueous **environments.

Question 8

Lipid molecules spontaneously form what structures in aqueous environments?

Answer 8

Micelles

Question 9

The fluidity of a membrane depends on what?

Answer 9

Its composition and the temperature

Question 10

What do lipid droplets store?

Answer 10

Neutral lipids such as triacylglycerides and cholesterol esters

Question 11

What are glycolipids?

Answer 11

Sugar-containing lipid molecules that are found exclusively in the non-cytosolic monolayer

Question 12

What are the different ways in which membrane proteins associate with the lipid bilayer?

Answer 12

1. a single alpha helix
2. multiple alpha helices
3. a beta barrel
4. anchored to cytosolic surface
5. by a covalently attached lipid chain
6. by an oligosaccharide linker
7. non-covalent interactions

Question 13

What membrane protein is this?

Answer 13

A single and multipass alpha helix

Question 14

What membrane protein is this?

Answer 14

A beta barrel

Question 15

What cytosolic membrane proteins are these?

Answer 15

An amphiphatic membrane protein and a protein attached to a prenyl group

Question 16

What exposed membrane protein is this?

Answer 16

A protein covalently linked via a disaccharide to phosphatidyl inositol, or known as a “GPI anchor”

Question 17

What non-covalently attached membrane proteins are these?

Answer 17

External and internal peripheral proteins

Question 18

The cell surface is usually coated with what?

Answer 18

Sugar residues, referred to as the carbohydrate layer

Question 19

What can be used to solubilise membrane proteins?

Answer 19

Detergents, which are small amphiphilic molecules of variable structure.

Question 20

Strong ionic detergents, such as ___, can solubilise even the most _____________ membrane proteins. This allows the proteins to be analysed by ___ ____________-____ electrophoresis.

Answer 20

Strong ionic detergents, such as SDS, can solubilise even the most **hydrophobic **membrane proteins. This allows the proteins to be analysed by SDS polyacrylamide-gel electrophoresis.

Question 21

How to cells restrict the lateral movement of membrane proteins?

Answer 21

From interactions of the plasma membrane with an underlying cytoskeleton.

Question 22

What filamentous protein is responsible for the biconcave shape in red blood cells?

Answer 22

Spectrin