The rate of movement of molecules or ions across a cell surface membrane is affected by the relative concentrations of the molecules or ions on either side of the membrane. The graphs below show the effect of concentration difference (the steepness of the concentration gradient) on three transport processes, namely diffusion, facilitated diffusion and active transport. 

a. With reference to the graphs, state what the three transport processes have in common.

b. Explain the rates of transport observed when the concentration difference is zero.

c. i. Which one of the processes would stop if a respiratory inhibitor were added?

ii. Explain your answer.

d. Explain the difference between the graphs for diffusion and facilitated diffusion.

Transcribed Image Text:

active transport diffusion facilitated diffusion Concentration difference Rate of transport