How does cholesterol affect membrane stability at high versus low temperature?

How does cholesterol affect membrane stability at high versus low temperature?

• A. holds together membrane at high temperature; keeps membrane fluid at low temperature
• B. increases permeability at all temperatures
• C. decreases membrane thickness at all temperatures
• D. has no effect on membrane properties

Answer: (A)

Cholesterol acts as a fluidity buffer for the membrane, helping it stay stable across temperature changes. The phospholipid bilayer becomes very fluid at high temperatures, which can undermine membrane integrity, and tends to solidify at low temperatures, which would block function. Cholesterol’s rigid ring structure fits between the fatty acid tails and modulates their movement: at high temperature it restricts excessive motion, helping “hold” the membrane together; at low temperature it prevents tight tail packing, keeping the membrane from solidifying and preserving needed fluidity. This dual role fits the idea of maintaining membrane stability by tuning fluidity with temperature. Other choices don’t capture this temperature-dependent effect and its impact on fluidity, permeability, or structure.

Cholesterol acts as a fluidity buffer for the membrane, helping it stay stable across temperature changes. The phospholipid bilayer becomes very fluid at high temperatures, which can undermine membrane integrity, and tends to solidify at low temperatures, which would block function. Cholesterol’s rigid ring structure fits between the fatty acid tails and modulates their movement: at high temperature it restricts excessive motion, helping “hold” the membrane together; at low temperature it prevents tight tail packing, keeping the membrane from solidifying and preserving needed fluidity. This dual role fits the idea of maintaining membrane stability by tuning fluidity with temperature. Other choices don’t capture this temperature-dependent effect and its impact on fluidity, permeability, or structure.