Membrane Structure

Question 1

What are the general functions of the cell membrane?

Answer 1

Transport, cell recognition, cellular communication and metabolic regulation

Question 2

What three molecules make up the sphingolipids group?

Answer 2

Ceramide, glycolipids, sphingomyelin

Question 3

What could the polar head groups in a phospholipid be made up of?

Answer 3

Choline, serine, ethanolamine, inositol

Question 4

Are substance evenly spread between the cytosolic and exoplasmic membrane?

Answer 4

No, some prefer being on one side

Question 5

Where does synthesis of a membrane take place, and give the steps

Answer 5

On the cytoplasmic side of the membrane

• newly synthesised phospholipid
• one side of the membrane is enlarged (it curves)
• the newly synthesised phospholipid is transferred to the luminal side

Question 6

What is an ATP-binding cassette transporter and what enzymes does it use?

Answer 6

ABC transporters allow for movement of phospholipids from one side of the membrane to the other
Flippase- outer to inner leaflet
Floppase- inner to outer leaflet
Scramblase- bidirectional movement

Question 7

What does amphipathic mean?

Answer 7

The have a hydrophilic and a hydrophobic part

Question 8

What are the three major lipids in the membrane?

Answer 8

Phospholipids, glycolipids and cholesterol

Question 9

Which of lateral movement and transverse movement is the fast and which is the slow?

Answer 9

Lateral is fast and transverse is slow

Question 10

How does temperature affect membrane fluidity?

Answer 10

High temp -> more energy ->more fluidity

Question 11

How does chain length affect membrane fluidity?

Answer 11

Higher chain length

Question 12

How does the degree and extent of saturation affect membrane fluidity?

Answer 12

More saturated means molecules closer together so less fluidity

Question 13

How does cholesterol content affect membrane fluidity?

Answer 13

At a low temperature membrane fluidity increases. At a high temperature membrane fluidity decreases

Question 14

What causes spur cell anaemia

Answer 14

Cholesterol content is increased by 25-65% leading to decreased membrane fluidity

Question 15

Give some functions of proteins in the cell membrane

Answer 15

Flexible, self-sealing, selectively permeable, defines boundaries and divide the internal spaces

Question 16

Give some functions of the integral membrane proteins

Answer 16

Strong non-covalent bonds (hard to separate), transmembrane domain often an alpha helix (Rgroups are hydrophobic)
Can be predicted from sequence
Mainly hydrophobic relationship with the lipids
Single or multi pass (can go through the membrane more than once)

Question 17

Give some structural features of the peripheral membrane proteins

Answer 17

Located on both the extra cellular and cytosolic membranes
Associated by non-covalent bonds
Easier to remove than protons

Question 18

What are lipid anchored membrane proteins

Answer 18

Covalently linked to a lipid molecule such as glycosylphosphatidylinositol or associated with a fatty acid

Question 19

Give some structural features of membrane carbohydrates

Answer 19

• Associated with both membrane lipids and proteins
• forms 2-8% of the membrane weight
• the majority of glycolipids and glycoproteins are externally facing
• often involved in cell-cell interactions or cellular recognition

Question 20

How are membrane carbohydrates important to RBCs?

Answer 20

• Blood group antigens are glycolipids

- In RBCs, 8% of the weight is carbohydrate