Practice question

MCQ

Question

Consider the following statements about transport across the plasma membrane:
I. A neutral solute may move from higher to lower concentration without expenditure of energy.
II. A polar molecule may require a carrier protein because it cannot readily cross the non-polar bilayer.
III. Movement from lower to higher concentration requires energy and represents active transport.
Which option correctly evaluates the statements?

Options

Choose one · Correct answer highlighted

Only statements I and II are correct. Statements I, II and III are correct. Correct Only statements II and III are correct. Only statement III is correct.

Explanation

Neutral solutes may diffuse down their concentration gradient without energy. Polar molecules require carrier proteins to cross the non-polar bilayer. Movement against a gradient is active transport and requires energy supplied through ATP.

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