Question

Which of the factor(s) determine the fluidity of the plasma membrane?

• A. Number of water molecules in the membrane
• B. Number of proteins
• C. Length of the lipids
• D. Number of unsaturated lipids

Answer 1

Answer: (C), (D)

Number of unsaturated lipids

A shorter chain length reduces the tendency of the hydrocarbon tails to interact with one another and therefore increases the fluidity of the bilayer. Each double bond in an unsaturated tail creates a small kink in the tail, which makes it more difficult for the tails to pack against one another.

For this reason, lipid bilayers that contain a large proportion of unsaturated hydrocarbon tails are more fluid than those with lower proportions.