Question

the presence of cholesterol molecules in plasma membranes is to ______ .
a allow the buildup of fats
b change the chemical nature of the membrane
c create a mosaic pattern
d stabilize the phospholipids at low temperatures

Explanation:

• Option A: Cholesterol in plasma membranes is not for allowing fat buildup. Plasma membrane's cholesterol has other functions related to membrane structure, so A is incorrect.
• Option B: Cholesterol does not change the chemical nature of the membrane. It interacts with phospholipids to affect membrane fluidity, not alter chemical nature, so B is wrong.
• Option C: The mosaic pattern of the plasma membrane (fluid - mosaic model) is due to the arrangement of phospholipids and proteins, not cholesterol creating it, so C is incorrect.
• Option D: At low temperatures, phospholipids tend to pack closely, and cholesterol molecules fit between phospholipid tails, preventing them from packing too tightly and stabilizing the membrane structure. So this option is correct.

Answer:

D. stabilize the phospholipids at low temperatures