tentang biology

'''Definition'''

''noun''

1. The [[passive]] [[movement]] of [[molecule]]s or particles along a [[concentration]] [[gradient]], or from [[region]]s of higher to [[region]]s of lower [[concentration]].

2. The [[spontaneous]] [[net]] [[movement]] of particles down their [[concentration]] [[gradient]] (i.e. difference in the [[concentrations]] of substances or [[molecule]]s between two [[area]]s).

3. (Cell biology): a type of [[passive]] [[transport]], therefore, it is a [[net]] [[movement]] of [[molecule]]s in and out of the [[cell]] across the [[cell membrane]] along a [[concentration]] [[gradient]].


'''Supplement'''

Unlike [[active transport]], diffusion does not involve [[chemical]] [[energy]]. When [[molecule]]s move ([[diffuse]]) via special [[transport]] [[protein]]s found within the [[cell membrane]], it is called [[facilitated diffusion]], otherwise it is only simple diffusion. An example of diffusion in biological system is diffusion of [[oxygen]] and [[carbon dioxide]] across the alveolar-capillary [[membrane]] in mammalian [[lung]]s.

Word origin: From Latin ''diffusionem'' (accusative of ''diffusio''), from verb ''diffundere''.

Related forms: diffusional (adjective).

Compare: [[active transport]], [[osmosis]].

See also: [[passive transport]].