Which statement about facilitated diffusion is correct?

Answer and explanation

Correct answer: A. It uses channel or carrier proteins and needs no ATP

  1. Step 1: Facilitated diffusion helps polar or charged molecules cross the membrane through proteins.
  2. Step 2: The movement follows the concentration gradient, so no ATP is needed.
Answer
It uses channel or carrier proteins and needs no ATP.
Why not the others: It uses ATP to move substances against a gradient: describes active transport. It moves lipid-soluble substances directly through the bilayer: describes simple diffusion. It moves water only, from high to low solute concentration: describes osmosis.

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