Editing Lactic acid fermentation (section)

{{Short description|Series of interconnected biochemical reactions}}
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[[Image:Lactic-acid-skeletal.svg|thumb|The L [[enantiomer]] of [[lactic acid]]]]
[[File:Output HyoqD2 (1).gif|thumb|This animation focuses on one molecule of [[glucose]] turning into pyruvate then into lactic acid. In the process there is one 6-carbon glucose molecule and 2 NAD+ molecules. 2 phosphates attach to the ends of the glucose molecule, then glucose is split into 2 3-carbon pyruvate precursors. Subsequently, NAD+ molecules are converted into 2 NADH and additional phosphate groups are attached to the carbons. Then ADP comes and takes the phosphates, creating 2 ATP molecules. The pyruvate is turned into 2 lactate molecules, which convert NADH back to NAD+. The process then repeats, starting with another glucose molecule.]]
'''Lactic acid fermentation''' is a metabolic process by which [[glucose]] or other [[hexose|six-carbon sugar]]s (also, [[disaccharides]] of six-carbon sugars, e.g. [[sucrose]] or [[lactose]]) are converted into cellular energy and the metabolite [[lactic acid|lactate]], which is lactic acid in solution. It is an [[Anaerobic organism#Metabolism|anaerobic]] [[fermentation]] reaction that occurs in some bacteria and [[animal cell]]s, such as [[muscle cell]]s.<ref name="fao1">{{cite book|last1=Battcock|first1=Mike|url=http://www.fao.org/3/x0560e/x0560e00.htm|title=Fermented Fruits and Vegetables: A Global Perspective|last2=Azam-Ali|first2=Sue|publisher=Food and Agriculture Organization of the United Nations|year=1998|isbn=92-5-104226-8|chapter=Bacterial Fermentations|access-date=2007-06-10|chapter-url=http://www.fao.org/docrep/x0560e/x0560e10.htm|archive-url=https://web.archive.org/web/20190224053324/http://www.fao.org/3/x0560e/x0560e00.htm|archive-date=2019-02-24|url-status=live}}</ref><ref name="ohio">{{cite web |last=Abedon |first=Stephen T. |url=http://www.mansfield.ohio-state.edu/~sabedon/biol1095.htm#lactic_acid_fermentation |title=Glycolysis and Fermentation |publisher=Ohio State University |date=1998-04-03 |access-date=2010-01-12 |url-status=dead |archive-url=https://web.archive.org/web/20100117221513/http://www.mansfield.ohio-state.edu/~sabedon/biol1095.htm#lactic_acid_fermentation |archive-date=2010-01-17 }}</ref><ref name="campbell">{{cite book |last1 = Campbell |first1 = Neil |last2 = Reece |first2 = Jane |authorlink1 = Neil Campbell (scientist) |authorlink2 = Jane Reece |title = Biology |url = https://archive.org/details/essentialbiology00camp_0 |url-access = registration |edition=7th |publisher = [[Benjamin Cummings]] |year = 2005 |isbn = 0-8053-7146-X}}</ref>{{page needed|date=August 2019}}

If oxygen is present in the cell, many organisms will bypass fermentation and undergo [[cellular respiration]]; however, [[facultative anaerobic organism]]s will both ferment and undergo respiration in the presence of oxygen.<ref name="campbell" /> Sometimes even when oxygen is present and aerobic metabolism is happening in the [[mitochondria]], if pyruvate is building up faster than it can be metabolized, the fermentation will happen anyway.

[[Lactate dehydrogenase]] catalyzes the interconversion of [[pyruvate]] and [[lactic acid|lactate]] with concomitant interconversion of NADH and [[Nicotinamide adenine dinucleotide|NAD<sup>+</sup>]].

In ''homolactic fermentation'', one molecule of glucose is ultimately converted to two molecules of lactic acid. ''Heterolactic fermentation'', by contrast, yields [[carbon dioxide]] and [[ethanol]] in addition to lactic acid, in a process called the [[phosphoketolase]] pathway.<ref name="fao1" />