fatty acid composition and membrane fluidity

Question 1

How do saturated fatty acids affect membrane fluidity?

Answer 1

Saturated fatty acids have straight chains that pack together tightly in the phospholipid bilayer, leading to a high density of phospholipids. This reduces membrane fluidity and flexibility, and lowers permeability to molecules.

Question 2

How do unsaturated fatty acids affect membrane fluidity?

Answer 2

Unsaturated fatty acids have one or more kinks in their hydrocarbon chains, which prevent them from packing as tightly. This increases membrane fluidity and flexibility, and raises permeability to certain molecules.

Question 3

Why is it important for cells to regulate the balance between saturated and unsaturated fatty acids?

Answer 3

Cells must regulate the ratio of saturated to unsaturated fatty acids to maintain membranes with the right properties:

• Fluidity: Membranes must remain fluid to allow for the movement of proteins and lipids.
• Strength and Integrity: The membrane must be strong enough to avoid perforation and maintain structural integrity.
• Permeability: The membrane must be permeable to allow essential molecules to pass, but not so porous that it loses selective control over what enters and exits the cell.

Question 4

How do environmental temperatures affect the fatty acid composition of membranes?

Answer 4

The ideal ratio of fatty acids varies depending on the environmental temperature:

Colder environments (e.g., Antarctic fish) require a higher proportion of unsaturated fatty acids in their membranes. This maintains fluidity and prevents the membrane from becoming too rigid and brittle in low temperatures.