SAT Subject Biology Practice Question 116: Answer and Explanation

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Question: 116

6. What prevents ions from crossing the plasma membrane via simple diffusion?

A. Ions are too large.
B. Ions carry a charge.
C. Ions are hydrophobic.
D. Ions do not produce a concentration difference.
E. Ions cannot interact with membrane-bound proteins.

Correct Answer: B


Because ions carry a charge, they cannot cross the hydrophobic cell membrane and so must be transported by facilitated diffusion via ion channels.

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