A cell is exposed to a sudden drop in temperature. How does cholesterol help maintain membrane fluidity under these conditions?

• A. Cholesterol increases the rigidity of the membrane by binding tightly to phospholipids.
• B. Cholesterol causes the membrane to become more permeable to ions.
• C. Cholesterol removes phospholipids from the membrane to increase fluidity.
• D. Cholesterol prevents the membrane from becoming too rigid by inserting itself between phospholipids, thus maintaining fluidity.

Answer: (D)