Membrane Transport Mechanisms · USMLE Step 1

Which of the following best describes what a uniporter does in the context of membrane transport?

  1. Moves two different molecules in opposite directions simultaneously
  2. Carries a single solute down its concentration gradient
  3. Uses ATP energy to pump a solute against its gradient
  4. Engulfs extracellular fluid and particles within vesicles
Show answer and explanation

Correct answer: Carries a single solute down its concentration gradient

A uniporter is a type of carrier protein that facilitates passive transport of one kind of solute down its concentration gradient — without coupling to another solute or using ATP.

Difficulty: Medium Question 22 of 24

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