Question

The lipid bilayer that makes up a cell membrane is composed of molecules like phospholipids that are synthesized from fatty acids. A phospholipid membrane undergoes a phase transition from solid-like to fluid-like when the temperature is raised above a melting temperature.
What can cause the melting temperature of a membrane to increase making it more solid-like at higher temperatures?
Select all that apply.

A. increasing the fraction of cis unsaturated fatty acids that make up the phospholipids

B. increasing cholesterol to disrupt the tight packing of the phospholipids fatty acyl chains

C. decreasing the fraction of saturated fatty acids that make up the phospholipids

D. increasing the fraction of saturated fatty acids that make up the phospholipids

E. decreasing cholesterol to increase the tight packing of the phospholipids fatty acyl chains

Answer 1

Correct options:

D. increasing the fraction of saturated fatty acids that make up the phospholipids

E. decreasing cholesterol to increase the tight packing of the phospholipids fatty acyl chains

T_m (melting temperature) refers to the phase transition. < T_m, the lipids are highly organized, this results tight packing of CH₃CO groups. > T_m, the lipids are less tightly packed, and the thickness of the lipid membrane decreases. The T_m increases with chain length, and decreases with increasing amounts of unsaturated fatty acids. Decreasing cholesterol will increase the tight packing and thereby increases T_m.

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