What is the force that drives passive diffusion of a molecule through a lipid bilayer?

Question

Quizplus · Accepted Answer

Passive diffusion is driven by a concentration gradient, which is the difference in concentration of the molecule between the two sides of the lipid bilayer. The molecule will move from an area of high concentration to an area of low concentration until equilibrium is reached. There is no energy input required from the ATP cycle, ion trapping, or polarity gradient for passive diffusion to occur.

What Is the Force That Drives Passive Diffusion of a Molecule