Multiple Choice
During hibernation in cold environments, what adaptation is most likely to occur in the phospholipid composition of a polar bear's cell membranes?
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6. The Membrane
Biological Membranes
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Which of the following is a function of cholesterol in the plasma membrane?
A
It serves as the primary site for protein synthesis.
B
It acts as a carrier for active transport of ions.
C
It modulates membrane fluidity by preventing extremes of rigidity or fluidity.
D
It directly catalyzes the formation of ATP.
Verified step by step guidance1
Understand the role of cholesterol in the plasma membrane: Cholesterol is a lipid molecule embedded within the phospholipid bilayer of the plasma membrane. It is not involved in protein synthesis, ion transport, or ATP formation directly.
Recall the structure of the plasma membrane: The plasma membrane is composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates. Cholesterol interacts with the fatty acid tails of phospholipids.
Learn how cholesterol modulates membrane fluidity: Cholesterol prevents the membrane from becoming too rigid at low temperatures by disrupting the packing of phospholipid tails. Conversely, it prevents the membrane from becoming too fluid at high temperatures by stabilizing the bilayer structure.
Eliminate incorrect options: Protein synthesis occurs in ribosomes, not cholesterol. Active transport of ions is facilitated by membrane proteins, not cholesterol. ATP formation is catalyzed by enzymes like ATP synthase, not cholesterol.
Conclude the correct function: Cholesterol's primary role in the plasma membrane is to modulate membrane fluidity, ensuring the membrane remains functional under varying temperature conditions.
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