AP Biologymediummcq1 pt

Winter wheat raises the fraction of unsaturated fatty acids in its membrane phospholipids as autumn cools. How does that shift preserve membrane function?

A.Kinked tails add negative charge that electrostatically repels invading ice crystals.
B.Double bonds soak up water, thinning the barrier so solutes travel less far.
C.Unsaturated tails lock onto transport proteins permanently, jamming channels open in the cold.
D.Double-bond kinks keep tails loosely packed, delaying cold-induced rigidification.

Explanation

Core Concept

Loose packing delays transition into a stiff, crystal-like array, so embedded transport proteins keep moving and the membrane stays functional at low temperature. Straight saturated chains would huddle together and rigidify the whole bilayer. Adjusting tail saturation is a standard cold-acclimation strategy.

Correct Answer

DDouble-bond kinks keep tails loosely packed, delaying cold-induced rigidification.

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