Question

Which of the following transport mechanisms is passive?

A) transport of sodium and potassium across the membrane by the Na+/K+ pump

B) countertransport of hydrogen ions with sodium

C) movement of calcium out of the cytosol

D) cotransport of glucose with sodium

E) movement of sodium through ion channels

Answer 1

The movement of sodium through ion channels is a passive transport mechanism because it does not require cellular energy and occurs down the electrochemical gradient.

Step-by-step explanation:

The option that represents a passive transport mechanism is E) movement of sodium through ion channels.

Passive transport mechanisms allow the movement of substances across cell membranes without the input of energy. Sodium ions move through cell membrane ion channels down their electrochemical gradient, which is a form of passive transport. This is in contrast to the sodium-potassium pump, which is an active transport mechanism that requires energy from ATP to move sodium and potassium ions against their concentration gradients.