Diffusion is the result of the random thermal movement of molecules, and it involves molecules spreading from regions of high concentration into regions of low concentration. The three types of diffusion are simple, channel and facilitated diffusion. The factors that influence the diffusion rate include the concentration gradient, molecule size, distance the molecule must travel, molecule solubility, temperature and surface area of the membrane.
Diffusion is typically noticed in liquids and gases, but it also occurs in some solids. In simple diffusion, a tiny nonpolar molecule moves through a lipid bilayer. This process is a type of passive transport, and it does not involve a protein. Osmosis is an example of simple diffusion. This is an important process in living organisms. Water solutions that are separated by a semipermeable membrane result in water diffusion through the membrane.
Channel diffusion involves channel proteins and results from the movement of material through an open aqueous pore. It is also classified as a type of passive transport, and it can be regulated, which means that ions and charged particles can move through the open pore.
Facilitated diffusion is a means of passive transport that relies on single transport protein carriers, which work on a bind, flip and release mechanism. It is nondiffusional, as the molecule moves along with the carrier.