Question

multiple choice question
which of the following transport mechanisms relies on concentration gradients of one substance to power the translocation of a different substance across a membrane?

primary active transport
facilitated diffusion
secondary active transport

Explanation:

• Primary active transport uses ATP (energy from hydrolysis) to move substances, not a concentration gradient of another substance.
• Facilitated diffusion is the passive transport of a substance via a protein, relying on its own concentration gradient, not another substance’s.
• Secondary active transport (cotransport) uses the concentration gradient of one substance (e.g., $Na^+$) to drive the transport of a different substance against its gradient.

Answer:

C. Secondary active transport