Apentix/AP Biology/Unit 1: Chemistry of Life/Question
AP Biologymediummcq1 pt

Cholesterol sits embedded among the phospholipids of animal membranes and buffers fluidity across temperatures. Which outcome matches its effect when the membrane gets too warm?

A.Its rigid ring system wedges between tails and restrains their movement, lowering fluidity
B.It liquefies the hydrophobic core and lets ions leak freely across the bilayer
C.It catalyzes the conversion of unsaturated tails into saturated tails
D.It forms water-filled pores that cool the membrane by evaporation

Explanation

Core Concept

Cholesterol's stiff four-ring structure inserts between neighboring phospholipids and physically blocks the wagging and sliding of fatty acid tails that would otherwise make a warm membrane overly fluid and leaky. At low temperature the same molecule has the opposite effect, keeping tails from packing into a crystal, which is why cholesterol is described as a fluidity buffer across a range of temperatures. It is not an enzyme, forms no pores, and does not open the core to ions.

Correct Answer

AIts rigid ring system wedges between tails and restrains their movement, lowering fluidity

More Unit 1: Chemistry of Life practice questions

Try a random question →

Practice more AP Biology questions with full explanations

Practice Unit 1: Chemistry of Life Questions →