Core component 3 - Permeability Of Membrane

Question 1

How do lipid-soluble substances move through the membrane?

Answer 1

Vitamin A and small molecules e.g. Oxygen dissolve in the phospholipid and diffuse across the membrane

Question 2

What type of substance moves through the membrane more easily and why?

Answer 2

Lipid-soluble substances because the membrane is hydrophobic.

Question 3

How do water-soluble substances move through the membrane ?

Answer 3

Polar molecules and ions cannot readily diffuse through the phospholipids and must pass through intrinsic protein molecules which form water-filled channels.

Therefore the membrane is selectively permeable to water and some solutes.