2.2

Question 1

Cell membranes

Answer 1

Phospholipid bilayer and associated protein.

Fluidity is crucial for membrane function and depends on temperature and lipid composition.

Cholesterol plays fundamental role - it regulates and maintains fluidity of cell membrane. Increases rigidity and reduces mobility.

Glycoproteins are membrane proteins with carbohydrates added.

Question 2

Membrane proteins

Answer 2

Integral membrane proteins - embedded in lipid bilayer,

Peripheral membrane proteins - not inserted in membrane, indirect association.

Amphipathic

Question 3

Transport across membrane

Answer 3

Selective permeability.

Only free small uncharged molecules can diffuse freely.
Large polar molecules are unable to diffuse across

Protein channels form pores in membrane allowing passage of molecules of suitable size/charge.

Carrier proteins bind and transport specific molecules like glucose 0 undergo conformational change.

Passive transport = no energy required down gradient
Active transport = energy required needs ATP. Low to high concentration.