In facilitated diffusion, the diffusion rate of a specific molecule across a membrane does not continue to increase as the concentration difference of the molecule across the membrane increases. This is the case because
A) facilitated diffusion requires the use of ATP.
B) as the concentration difference increases, molecules interfere with one another.
C) the carrier proteins are saturated.
D) the transport protein must be of the channel type.
E) the diffusion constant depends on the concentration difference.

Question

Quizplus · Accepted Answer

Facilitated diffusion relies on carrier proteins to transport molecules across the membrane. These carrier proteins become saturated as the concentration of the molecule they transport increases, meaning that once all the transport proteins are in use, the rate of diffusion cannot increase any further. Therefore, option C is correct. Options A, B, D, and E are incorrect as they do not explain the saturation of carrier proteins in facilitated diffusion.

In Facilitated Diffusion, the Diffusion Rate of a Specific Molecule