Which statement about active transport is true?

• A. It moves substances down their gradient using energy.
• B. It moves substances with their gradient without energy.
• C. It uses energy to move substances against their gradient.
• D. It relies on passive diffusion to transport solutes.

Answer: (C)

Active transport is all about using energy to push substances uphill, against their concentration or electrochemical gradient. This energy can come from ATP hydrolysis or from coupling to an existing ion gradient, powering pumps and secondary transporters. That’s why the statement that describes using energy to move substances against their gradient is the correct one. The other descriptions depict passive processes that move substances down their gradient or rely on diffusion, which don’t require energy and aren’t active transport.