Membrane Transport Mechanisms · USMLE Step 1

Which of the following is true about ion channels used in facilitated diffusion?

  1. They transport ions against their electrochemical gradient using ATP
  2. They are always open, allowing unrestricted ion movement
  3. They are selective for specific ions and are usually gated
  4. They transport only large uncharged organic molecules
Show answer and explanation

Correct answer: They are selective for specific ions and are usually gated

Ion channels are selective for particular ions (e.g., Na⁺, K⁺, Ca²⁺) and may be gated (e.g., by voltage or ligands), enabling controlled passive movement down the electrochemical gradient without energy input.

Difficulty: Medium Question 13 of 24

Practice all 24 Membrane Transport Mechanisms questions

Keep practicing

More Membrane Transport Mechanisms questions