Which of the Following Cross- Membrane Transport Mechanisms Occur Without

Question

Which of the following cross- membrane transport mechanisms occur without expenditure of energy?
A) antiporter
B) channel
C) cotransporter
D) pump
E) symporter

Accepted Answer

Channel proteins facilitate the movement of molecules or ions down their concentration gradients by forming a relatively open tunnel through the membrane. This does not require the expenditure of energy. The other options (antiporter, cotransporter, pump, and symporter) all require the expenditure of energy in some form (such as ATP hydrolysis) to move molecules or ions against their concentration gradients.