Editing Molecular diffusion (section)

== Significance ==
[[File:Diffusion (1).png|thumb|280px|Schematic representation of mixing of two substances by diffusion]]
Diffusion is part of the [[transport phenomena]]. Of mass transport mechanisms, molecular diffusion is known as a slower one.

=== Biology ===
In [[cell biology]], diffusion is a main form of transport for necessary materials such as [[amino acid]]s within cells.<ref>{{cite book | last = Maton | first = Anthea |author2=Jean Hopkins |author3=Susan Johnson |author4=David LaHart |author5=Maryanna Quon Warner |author6=Jill D. Wright | title = Cells Building Blocks of Life | publisher = Prentice Hall | year = 1997 | location = Upper Saddle River, New Jersey | pages = [https://archive.org/details/cellsbuildingblo00mato/page/66 66–67] | isbn = 978-0-13-423476-2 | url =https://archive.org/details/cellsbuildingblo00mato| url-access = registration }}</ref> Diffusion of solvents, such as water, through a [[semipermeable membrane]] is classified as [[osmosis]].

[[Metabolism]] and [[Respiration (physiology)|respiration]] rely in part upon diffusion in addition to bulk or active processes. For example, in the [[pulmonary alveolus|alveoli]] of [[mammal]]ian [[lung]]s, due to differences in partial pressures across the alveolar-capillary membrane, [[oxygen]] diffuses into the blood and [[carbon dioxide]] diffuses out. Lungs contain a large surface area to facilitate this gas exchange process.