Question

which transport system can move an ion across the cell membrane against (up) its concentration gradient using atp?
the sodium-potassium pump
facilitated diffusion using a carrier protein
osmosis in a hypertonic solution
simple diffusion

Explanation:

Transport against a concentration gradient (uphill) that uses ATP is active transport. The sodium-potassium pump is an example of primary active transport that uses ATP to move Na⁺ and K⁺ against their concentration gradients. Facilitated diffusion, osmosis, and simple diffusion are all passive processes that move substances down their concentration gradients without using ATP.

Answer:

A. The Sodium-Potassium Pump