Lipid Asymmetry

Question 1

What is lipid asymmetry caused by?

Answer 1

Different head groups on different sides of membrane

Question 2

Describe lipid composition of erythrocyte membrane

Answer 2

• 50% cholesterol
• High concentration of PC and SM lipids in outer leaflets
• High concentration of PS and PE lipids in inner leaflet

Question 3

What happens to PS in animal cells when cells undergo apoptosis?

Answer 3

PS lipids translocate to extracellular monolayer to act as a signal to neighbouring cells (e.g. macrophages to phagocytose the dead cell)

Question 4

What does the movement of PS lipids occur via?

Answer 4

Scramblases

Question 5

How are glycolipids oriented?

Answer 5

Towards the exterior of the cell (outer leaflet)

Question 6

How are 2nd messengers oriented?

Answer 6

Towards the interior of the cell

Question 7

Why does lipid interdigitation occur?

Answer 7

Due to the lipid length asymmetry in membranes

Question 8

What is purpose of interdigitation?

Answer 8

Couples the 2 leaflets together and decreases the lipid thickness

Question 9

What can changes in lipid composition lead to?

Answer 9

Diseases (such as cancer or type 2 diabetes)

Question 10

What is noticeable in lung cancer?

Answer 10

• Differences between glycerophospholipid profiles of tumour tissues and normal tissues
• Some PI species higher in tumour samples
• Sphingomyelin species decreased in tumour samples

Question 11

What is noticeable in breast cancer?

Answer 11

PI, PE, PC and SM lipids were higher in tumour tissues than healthy controls

Question 12

What diseases is ceramide increased in?

Answer 12

Type 2 diabetes, Alzheimers, Cystic Fibrosis