Which of the following statements correctly distinguishes active transport across a cell membrane from facilitated diffusion?
Answer and explanation
Correct answer: D. Active transport operates against a concentration gradient and requires ATP hydrolysis
- Step 1: Both facilitated diffusion and active transport require specific transmembrane carrier or channel proteins.
- Step 2: Facilitated diffusion moves solutes down their chemical or electrical electrochemical gradient without expenditure of metabolic energy.
- Step 3: Active transport pumps solutes uphill against their electrochemical gradient, coupling the process directly to ATP hydrolysis or an ion gradient.
Answer
Active transport operates against a concentration gradient and requires ATP hydrolysis.
Why not the others: Facilitated diffusion operates down a concentration gradient, never against it; Active transport is an active exergonic-coupled process, not passive; Facilitated diffusion does not consume metabolic ATP.
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