Editing Intracellular pH (section)

== Homeostasis ==
Intracellular pH is typically lower than [[extracellular]] pH due to lower concentrations of HCO<sub>3</sub><sup>−</sup>.<ref>{{cite journal |vauthors=Flinck M, Kramer SH, Pedersen SF |title=Roles of pH in control of cell proliferation |journal=Acta Physiol (Oxf) |volume=223 |issue=3 |pages=e13068 |date=July 2018 |pmid=29575508 |doi=10.1111/apha.13068 |s2cid=4874638 }} {{verify source |date=September 2019 |reason=This ref was deleted Special:Diff/901265489 by a bug in VisualEditor and later restored by a bot from the original cite located at Special:Permalink/901264743 cite #5 - verify the cite is accurate and delete this template. [[User:GreenC bot/Job 18]]}}</ref> A rise of extracellular (e.g., [[Serum (blood)|serum]]) [[partial pressure]] of [[carbon dioxide]] ([[PCO2|pCO<sub>2</sub>]]) above 45&nbsp;[[mmHg]] leads to formation of [[carbonic acid]], which causes a decrease of pH<sub>i</sub> as it [[Dissociation (chemistry)|dissociates]]:<ref>Flinck M, Kramer SH, Pedersen SF (July 2018). "Roles of pH in control of cell proliferation". ''Acta Physiol (Oxf)''. '''223''' (3): e13068. [[Digital object identifier|doi]]:10.1111/apha.13068. [[PubMed Identifier|PMID]] 29575508.</ref>

: H<sub>2</sub>O + CO<sub>2</sub> {{eqm}} H<sub>2</sub>CO<sub>3</sub> {{eqm}} H<sup>+</sup> + HCO<sub>3</sub><sup>–</sup>

Since biological cells contain fluid that can act as a buffer, pH<sub>i</sub> can be maintained fairly well within a certain range.<ref>{{cite journal | vauthors = Slonczewski JL, Fujisawa M, Dopson M, Krulwich TA | title = Cytoplasmic pH measurement and homeostasis in bacteria and archaea | journal = Advances in Microbial Physiology | volume = 55 | pages = 1–79, 317 | date = 2009 | pmid = 19573695 | doi = 10.1016/S0065-2911(09)05501-5 | isbn = 9780123747907 }}</ref> Cells adjust their pH<sub>i</sub> accordingly upon an increase in acidity or basicity, usually with the help of CO<sub>2</sub> or HCO<sub>3</sub><sup>–</sup> sensors present in the membrane of the cell.<ref name=":0" /> These sensors can permit H+ to pass through the cell membrane accordingly, allowing for pH<sub>i</sub> to be interrelated with extracellular pH in this respect.<ref>{{cite journal | vauthors = Jensen FB | title = Red blood cell pH, the Bohr effect, and other oxygenation-linked phenomena in blood O2 and CO2 transport | journal = Acta Physiologica Scandinavica | volume = 182 | issue = 3 | pages = 215–27 | date = November 2004 | pmid = 15491402 | doi = 10.1111/j.1365-201X.2004.01361.x }}</ref>

Major intracellular buffer systems include those involving proteins or phosphates. Since the proteins have acidic and basic regions, they can serve as both proton donors or acceptors in order to maintain a relatively stable intracellular pH. In the case of a phosphate buffer, substantial quantities of weak acid and conjugate weak base (H<sub>2</sub>PO<sub>4</sub><sup>–</sup> and HPO<sub>4</sub><sup>2–</sup>) can accept or donate protons accordingly in order to conserve intracellular pH:<ref>{{cite web | first = Michael J | last = Bookallil | name-list-style = vanc  |url= http://www.anaesthesia.med.usyd.edu.au/resources/lectures/acidbase_mjb/control.html#co2control|title= Acid-Base: pH of the Blood - 3 - Control mechanisms  | publisher = The University of Sydney Nuffield Department of Anaesthetics | work = Lectures and Study Notes Listing |access-date=2019-05-28}}</ref><ref>{{cite journal | vauthors = Burton RF | title = Intracellular buffering | journal = Respiration Physiology | volume = 33 | issue = 1 | pages = 51–8 | date = April 1978 | pmid = 27854 | doi = 10.1016/0034-5687(78)90083-X }}</ref>

:OH<sup>–</sup> + H<sub>2</sub>PO<sub>4</sub><sup>–</sup> {{eqm}} H<sub>2</sub>O + HPO<sub>4</sub><sup>2–</sup>
:H<sup>+</sup> + HPO<sub>4</sub><sup>2–</sup> {{eqm}} H<sub>2</sub>PO<sub>4</sub><sup>–</sup>