Apentix/AP Biology/Unit 2: Cell Structure and Function/Question
AP Biologyhardmcq1 pt

For solutes moving purely by diffusion, the average time to reach a target rises with the square of the distance traveled. A mutant spherical cell triples its radius. Which consequence follows for its interior chemistry?

A.The cell center receives diffusing nutrients about nine times more slowly, favoring smaller cell dimensions
B.Delivery time to the center triples, exactly matching the radius change
C.The cell compensates by speeding the diffusion of every solute it uses
D.Nutrient distribution becomes uniform once the cell passes a size threshold

Explanation

Core Concept

Diffusion time scales with distance squared, so tripling the travel distance lengthens delivery time roughly ninefold. Cytoplasm near the surface still feeds promptly, but the core waits long enough for consumption to outrun arrival, opening depletion zones. This scaling pressure explains why large cells depend on internal transport systems or elongated shapes rather than on diffusion alone.

Correct Answer

AThe cell center receives diffusing nutrients about nine times more slowly, favoring smaller cell dimensions

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