Facilitated diffusion differs from ordinary diffusion in that
A)facilitated diffusion consumes no ATP.
B)facilitated diffusion moves molecules from an area of higher concentration to lower concentration.
C)the rate of molecular movement is limited by the number of available carrier molecules.
D)facilitated diffusion never eliminates the concentration gradient.
E)the rate of molecular movement is not limited by the number of available carrier molecules.

Question

Quizplus · Accepted Answer

Facilitated diffusion requires the use of carrier or channel proteins to move molecules across the membrane, and the rate of movement is limited by the number of available proteins. This distinguishes it from ordinary diffusion, which occurs without the use of any proteins or other membrane-bound structures. Choice A is also true, but it does not distinguish facilitated diffusion from ordinary diffusion. Choice B and D are characteristics of both types of diffusion. Choice E is false, as the rate of movement in facilitated diffusion is indeed limited by the availability of carrier/transport proteins.

Facilitated Diffusion Differs from Ordinary Diffusion in That