What is the primary role of cholesterol in animal cell plasma membranes at low physiological temperatures?
Answer and explanation
Correct answer: D. Preventing close packing of phospholipid fatty acid chains to maintain membrane fluidity
Cholesterol acts as a bidirectional membrane fluidity buffer. At lower temperatures, its rigid steroid ring system inserts between hydrocarbon tails, preventing them from clustering and crystallizing, which preserves membrane fluidity. It does not increase permeability to polar solutes, anchor actin directly, or catalyze flippase reactions.
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