Editing Osmotic pressure (section)

== Applications ==
[[Image:Osmotic pressure on blood cells diagram.svg|thumb|upright=1.15|Osmotic pressure on red blood cells]]
Osmotic pressure measurement may be used for the determination of [[molecular weight]]s.

Osmotic pressure is an important factor affecting biological cells.<ref>{{cite journal | vauthors = Esteki MH, Malandrino A, Alemrajabi AA, Sheridan GK, Charras G, Moeendarbary E | title = Poroelastic osmoregulation of living cell volume | language = English | journal = iScience | volume = 24 | issue = 12 | pages = 103482 | date = December 2021 | pmid = 34927026 | pmc = 8649806 | doi = 10.1016/j.isci.2021.103482 | bibcode = 2021iSci...24j3482E }}</ref> [[Osmoregulation]] is the [[homeostasis]] mechanism of an organism to reach balance in osmotic pressure.

*[[Tonicity#Hypertonic solution|Hypertonicity]] is the presence of a solution that causes cells to shrink.
*[[Tonicity#Hypotonicity|Hypotonicity]] is the presence of a solution that causes cells to swell.
*[[Tonicity#Isotonicity|Isotonicity]] is the presence of a solution that produces no change in cell volume.

When a [[biological tissue|biological]] [[cell (biology)|cell]] is in a hypotonic environment, the cell interior accumulates water, water flows across the [[cell membrane]] into the cell, causing it to expand. In [[plant cell]]s, the [[cell wall]] restricts the expansion, resulting in pressure on the cell wall from within called [[turgor pressure]]. Turgor pressure allows [[herbaceous plant]]s to stand upright. It is also the determining factor for how plants regulate the aperture of their [[stomata]]. In animal cells excessive osmotic pressure can result in [[cytolysis]] due to the absence of a cell wall.

Osmotic pressure is the basis of filtering ("[[reverse osmosis]]"), a process commonly used in [[water purification]]. The water to be purified is placed in a chamber and put under an amount of pressure greater than the osmotic pressure exerted by the water and the solutes dissolved in it. Part of the chamber opens to a differentially permeable membrane that lets water molecules through, but not the solute particles. The osmotic pressure of ocean water is approximately 27 [[Atmosphere (unit)|atm]]. Reverse osmosis [[desalination|desalinates]] fresh water from [[seawater|ocean salt water]] and is applied globally on a very large scale.