Intensity of facilitated diffusion

Question

How does intensity of facilitated diffusion differ in relation to the concentration of the moved substance? Also explain the limiting factor?

Answer 1

Similar to simple diffusion facilitated diffusion is more intense whenever the concentration gradient of the substance rises and less intense whenever the gradient lessens.

In facilitated diffusion though there is a limiting factor: the quantity of the permeases that facilitate the transport via the membrane. Even in a condition in which the concentration gradient of the diffusing substance rises, when there are not adequate permeases to execute the transport there will be no raise in the intensity of the diffusion. This condition is termed as saturation of the transport proteins and it symbolizes the point at which the maximum transport capacity of the substance across the membrane is attained.