Apentix/AP Biology/Unit 2: Cell Structure and Function/Question

AP Biologymediummcq1 pt

Which transport example relies on direct ATP hydrolysis to move a solute against its gradient?

A.The sodium-potassium pump, which exports three Na+ while importing two K+

B.Water movement through aquaporin channels

C.Glucose entry through a passive carrier protein

D.Osmotic swelling of a cell in pondwater

Explanation

Core Concept

The Na+/K+-ATPase hydrolyzes ATP itself, using the released phosphate to drive conformational changes that push each ion uphill against its electrochemical gradient. This primary active transport sets up the sodium gradient that secondary transport later exploits. Water through aquaporins, glucose through passive carriers, and osmosis all follow existing gradients and consume no ATP, so the pump is the only active example listed.

Correct Answer

AThe sodium-potassium pump, which exports three Na+ while importing two K+

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