Editing Bicarbonate (section)

==Physiological role==
[[File:Riassorbimento bicarbonati e respirazione cellulare.svg|450px|thumbnail|right|{{CO2}} produced as a waste product of the oxidation of sugars in the mitochondria reacts with water in a reaction catalyzed by [[carbonic anhydrase]] to form {{chem2|H2CO3}}, which is in equilibrium with the cation {{H+}} and anion {{chem2|HCO3-}}. It is then carried to the lung, where the reverse reaction occurs and {{CO2}} gas is released. In the kidney (left), cells (green) lining the proximal tubule conserve bicarbonate by transporting it from the glomerular filtrate in the lumen (yellow) of the nephron back into the blood (red). The exact stoichiometry in the kidney is omitted for simplicity.]]{{clear left}}
Bicarbonate is a vital component of the [[pH]] [[Buffer solution|buffering system]]<ref name="veq"/> of the human body (maintaining [[acid–base homeostasis]]). 70%–75% of {{CO2}} in the body is converted into [[carbonic acid]] ({{chem2|H2CO3}}), which is the [[conjugate acid]] of {{chem2|HCO3-}} and can quickly turn into it.{{cn|date=February 2024}}

With carbonic acid as the [[Reaction intermediate|central intermediate]] [[Chemical species|species]], bicarbonate – in conjunction with water, [[hydronium|hydrogen ions]], and [[carbon dioxide]] – forms this buffering system, which is maintained at the volatile equilibrium<ref name="veq"/> required to provide prompt resistance to pH changes in both the acidic and [[Base (chemistry)|basic]] directions. This is especially important for protecting [[Tissue (biology)|tissues]] of the [[central nervous system]], where pH changes too far outside of the normal range in either direction could prove disastrous (see [[acidosis]] or [[alkalosis]]). Recently it has been also demonstrated that cellular bicarbonate metabolism can be regulated by mTORC1 signaling.<ref>{{cite journal|vauthors = Ali E, Liponska A, O'Hara B, Amici D, Torno M, Gao P, Asara J, Yap M-N F, Mendillo M, Ben-Sahra I|title = The mTORC1-SLC4A7 axis stimulates bicarbonate import to enhance de novo nucleotide synthesis|journal = Molecular Cell|volume = 82|issue = 1|pages = 3284–3298.e7|date = June 2022|doi = 10.1016/j.molcel.2022.06.008|pmid = 35772404|pmc = 9444906}}</ref>

Additionally, bicarbonate plays a key role in the digestive system. It raises the internal pH of the stomach, after highly acidic digestive juices have finished in their digestion of food. Bicarbonate also acts to regulate pH in the small intestine. It is released from the [[pancreas]] in response to the hormone [[secretin]] to neutralize the acidic [[chyme]] entering the [[duodenum]] from the stomach.<ref>Berne & Levy, ''Principles of Physiology''</ref>