Question

In facilitated diffusion, the diffusion rate of a specific molecule across a membrane does not continue to increase as the molecules concentration difference across the membrane increases beyond a certain point. The reason is that:

a. Facilitated diffusion is an active process
b. The membrane becomes saturated with the molecule
c. The molecule is actively transported
d. The concentration difference is too low

Answer 1

The diffusion rate in facilitated diffusion does not continue to increase beyond a certain point because the transport proteins in the membrane become saturated with the molecule causing a maximum rate of transport.

Step-by-step explanation:

In facilitated diffusion, the diffusion rate of a specific molecule across a membrane does not continue to increase as the molecule's concentration difference across the membrane increases beyond a certain point. The reason for this is that the membrane becomes saturated with the molecule. Similar to enzyme catalysis, there is a maximum rate of transport (Vmax) when all the transport proteins are occupied by the molecules, exhibiting a saturation phenomenon. This process is passive and does not require energy; it is facilitated by membrane proteins that provide a way for certain molecules, which cannot pass freely through the lipid bilayer due to their size, charge, or polarity, such as glucose, to diffuse down their concentration gradient.