Membrane Transport Mechanisms · USMLE Step 1

How does the presence of cholesterol in the plasma membrane influence membrane transport properties?

  1. It makes the membrane freely permeable to charged ions
  2. It reduces membrane fluidity and passive leakiness
  3. It acts as a channel protein for facilitated diffusion
  4. It actively pumps solutes across the bilayer using ATP
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Correct answer: It reduces membrane fluidity and passive leakiness

Cholesterol stabilizes and stiffens the phospholipid bilayer, reducing its passive permeability and making the membrane less leaky, thus influencing the selectivity and control of transport processes.

Difficulty: Medium Question 12 of 24

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