MCAT Biochemistry Question 110: Answer and Explanation

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Question: 110

5. The dynamic properties of molecules in the cell membrane are most rapid in:

  • A. phospholipids moving within the plane of the membrane.
  • B. phospholipids moving between the planes of the membrane.
  • C. proteins moving within the plane of the membrane.
  • D. proteins exiting the cell through exocytosis.

Correct Answer: A

Explanation:

Movement of individual molecules in the cell membrane will be affected by size and polarity, just as with diffusion. Lipids are much smaller than proteins in the plasma membrane and will move more quickly. Lipids will move fastest within the plane of the cell membrane because the polar head group does not need to pass through the hydrophobic tail region in the same way that it would if it were moving between the membrane planes.

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