Question

ANSWER QUICKLY!!! TIMED!!! A simple image of a plasma membrane is shown.

The shape of the hydrophobic "tails” of lipids in a membrane affects the packing of the lipids in a lateral, or sideways, direction. Unsaturated fatty acids in the lipid tail sometimes have a kinky shape (refer to the diagram). Cholesterol is another lipid and a constituent of membrane that affects the fluidity (the ability of molecules to move freely) of membranes depending on temperature. The movements of membrane integral proteins are positively affected by the movements of lipids.



At 37oC, how is the lateral movement of membrane integral proteins affected by an increase in unsaturated tails or an increase of cholesterol percentage?



A) Increased when percentage of unsaturated tails increases; increased when percentage of cholesterol increases.

B) Increased when percentage of unsaturated tails increases; decreased when percentage of cholesterol increases.

C) Decreased when percentage of unsaturated tails increases; increased when percentage of cholesterol increases.

D) Decreased when percentage of unsaturated tails increases; decreased when percentage of cholesterol increases.

Answer 1

At 37ºC the lateral movement of integral membrane proteins increases when the percentage of unsaturated tails increases and increases when the percentage of cholesterol increases, as shown in option A.

What is cholesterol?

• It is a fatty compound that exists in organisms.
• It is a long-chain lipid.

The lateral movement of integral proteins increases when the percentage of unsaturated tails increases because unsaturated fatty acids have the capacity for great flexibility, which allows spaces to be created between the tails, allowing lateral movement, without them tangling together.

This lateral movement also increases with a higher percentage of cholesterol because cholesterol is a type of natural buffer at high temperatures, which allows the membrane to remain fluid, preventing excessive movements.