Diffusion is the net movement of molecules from an area where they are at a higher concentration to areas where they are at a lower concentration. This is due to the random movement of the molecules.

This movement is against the concentration gradient so the transport proteins require an energy supply. Energy is provided by the breakdown of ATP inside the cell. This diagram shows molecules ...

Brownian motion refers to the erratic and random movement of microscopic particles within a fluid, as they collide with the faster-moving molecules of the fluid medium. This phenomenon was first ...