Carrier-mediated transport
A) involves a specific membrane protein that serves as a carrier molecule.
B) always moves substances against a concentration gradient.
C) always requires energy expenditure.
D) two of these answers.
E) all of these answers.

Question

Quizplus · Accepted Answer

Carrier-mediated transport involves a specific membrane protein that serves as a carrier molecule. This protein binds to a specific molecule or ion and transports it across the membrane.

Answer: D
 Carrier-mediated transport does not always move substances against a concentration gradient, and it does not always require energy expenditure. Some types of carrier-mediated transport, such as facilitated diffusion, move substances down their concentration gradient without requiring energy input. However, active transport does require energy input to move substances against their concentration gradient.

Carrier-Mediated Transport