Biological membranes

Question 1

How does high temperature affect the permeability of membranes?

Answer 1

Phospholipids have greater kinetic energy and move around more, increasing fluidity.

This could alter the function of membrane embedded proteins if they move, altering the rate of reaction they catalyse

Question 2

What happens to membranes when temperature drops?

Answer 2

Saturated fatty acids become compressed

Unsaturated fatty acids push the adjacent phospholipids away due to the kink in their tail, maintaining fluidity

Proportion of saturated and unsaturated fatty acids determines fluidity

Question 3

How does cholesterol regulate fluidity?

Answer 3

Prevent the phospholipids packing too close together

Question 4

What is active transport?

Answer 4

The movement of substances against their concentration gradient across a cell membrane, using ATP and protein carriers.

Question 5

How do carrier proteins work?

Answer 5

The proteins have specific regions which combine with ions.

Hydrolysis of ATP allows the protein to undergo a conformational change, carrying an ion from one side to the other.