Editing Cytosol (section)

===Concentration gradients===
Although small molecules [[diffusion|diffuse]] rapidly in the cytosol, concentration gradients can still be produced within this compartment. A well-studied example of these are the "calcium sparks" that are produced for a short period in the region around an open [[calcium channel]].<ref>{{cite journal |vauthors=Wang SQ, Wei C, Zhao G |title=Imaging microdomain Ca2+ in muscle cells |journal=Circ. Res. |volume=94 |issue=8 |pages=1011–22 |date=April 2004 |pmid=15117829 |doi=10.1161/01.RES.0000125883.68447.A1 |doi-access=free }}</ref> These are about 2&nbsp;[[micrometre]]s in diameter and last for only a few [[millisecond]]s, although several sparks can merge to form larger gradients, called "calcium waves".<ref>{{cite journal |author=Jaffe LF |title=Classes and mechanisms of calcium waves |journal=[[Cell Calcium]] |volume=14 |issue=10 |pages=736–45 |date=November 1993 |pmid=8131190 |doi=10.1016/0143-4160(93)90099-R}}</ref> Concentration gradients of other small molecules, such as [[oxygen]] and [[adenosine triphosphate]] may be produced in cells around clusters of [[mitochondrion|mitochondria]], although these are less well understood.<ref>{{cite journal | author=Aw, T.Y. |year=2000 |title=Intracellular compartmentation of organelles and gradients of low molecular weight species |journal=Int Rev Cytol |volume=192 |pages=223–53 |doi=10.1016/S0074-7696(08)60528-8 |pmid=10553281 | series=International Review of Cytology | isbn=978-0-12-364596-8}}</ref><ref>{{cite journal |vauthors=Weiss JN, Korge P |title=The cytoplasm: no longer a well-mixed bag |journal=Circ. Res. |volume=89 |issue=2 |pages=108–10 |date=20 July 2001|pmid=11463714 |doi=10.1161/res.89.2.108 |doi-access=free }}</ref>