The wide occurrence of glycolysis in other species indicates that it is an ancient metabolic pathway.<ref>{{cite journal | vauthors = Romano AH, Conway T | title = Evolution of carbohydrate metabolic pathways | journal = Research in Microbiology | volume = 147 | issue = 6–7 | pages = 448–455 | year = 1996 | pmid = 9084754 | doi = 10.1016/0923-2508(96)83998-2 | doi-access = free }}</ref> Indeed, the reactions that make up glycolysis and its parallel pathway, the [[pentose phosphate pathway]], can occur in the [[Great Oxygenation Event|oxygen-free conditions]] of the [[Archean]] oceans, also in the absence of enzymes, catalyzed by metal ions, meaning this is a plausible prebiotic pathway for [[abiogenesis]].<ref>{{cite journal | vauthors = Keller MA, Turchyn AV, Ralser M | title = Non-enzymatic glycolysis and pentose phosphate pathway-like reactions in a plausible Archean ocean | journal = Molecular Systems Biology | volume = 10 | issue = 4 | pages = 725 | date = April 2014 | pmid = 24771084 | pmc = 4023395 | doi = 10.1002/msb.20145228 }}</ref>

<div style="display:flex; flex-flow:row wrap; border:1px solid #a79c83; margin:1em" class="skin-invert-image>

[[File:Glycolysis.svg|thumb|445x445px|class=skin-invert-image|Glycolysis pathway overview]]

Charges are balanced by the difference between ADP and ATP. In the cellular environment, all three hydroxyl groups of ADP dissociate into −O⁻ and H⁺, giving ADP³⁻, and this ion tends to exist in an ionic bond with Mg²⁺, giving ADPMg⁻. ATP behaves identically except that it has four hydroxyl groups, giving ATPMg²⁻. When these differences along with the true charges on the two phosphate groups are considered together, the net charges of −4 on each side are balanced.{{cn|date=September 2024}}

| [[File:Metabolism of common monosaccharides, and related reactions.png|none|1000px|class=skin-invert-image]]

The pathwaymodern understanding of glycolysisthe aspathway itof is known todayglycolysis took almost 100 years to fully elucidatelearn.<ref name="pmid12722184">{{cite journal | vauthors = Barnett JA | title = A history of research on yeasts 5: the fermentation pathway | journal = Yeast | volume = 20 | issue = 6 | pages = 509–543 | date = April 2003 | pmid = 12722184 | doi = 10.1002/yea.986 | s2cid = 26805351 | doi-access = free }}</ref> The combined results of many smaller experiments were required in order to understand the intricacies of the entire pathway.

The first steps in understanding glycolysis began in the nineteenth19th century with the wine industry. For economic reasons, the French wine industry sought to investigate why wine sometimes turned distasteful, instead of fermenting into alcohol. The French scientist [[Louis Pasteur]] researched this issue during the 1850s, and the results of his experiments began the long road to elucidating the pathway of glycolysis.<ref>{{cite web |title=Louis Pasteur and Alcoholic Fermentation |url=http://www.pasteurbrewing.com/articles/beer-wine-fermentation.html |website=www.pasteurbrewing.com |access-date=2016-02-23 |archive-url=https://web.archive.org/web/20110113030412/http://www.pasteurbrewing.com/articles/beer-wine-fermentation.html |archive-date=2011-01-13 |url-status=dead }}</ref> His experiments showed that alcohol fermentation occurs by the action of living [[microorganism]]s, yeasts, and that yeast's glucose consumption decreased under aerobic conditions of fermentation, in comparison to anaerobic conditions (the [[Pasteur effect]]).<ref>{{cite journal | vauthors = Alba-Lois L, Segal-Kischinevzky C | title = Yeast fermentation and the making of beer and wine. | journal = Nature Education | date = January 2010 | volume = 3 | issue = 9 | pages = 17 | url = http://www.nature.com/scitable/topicpage/yeast-fermentation-and-the-making-of-beer-14372813 }}</ref>

Insight into theThe component steps of glycolysis were providedfirst analysed by the non-cellular fermentation experiments of [[Eduard Buchner]] during the 1890s.<ref>{{cite journal | vauthors = Kohler R | title = The background to Eduard Buchner's discovery of cell-free fermentation | journal = Journal of the History of Biology | volume = 4 | issue = 1 | pages = 35–61 | date = 1971-03-01 | pmid = 11609437 | doi = 10.1007/BF00356976 | s2cid = 46573308 }}</ref><ref>{{cite web |title=Eduard Buchner - Biographical |url=https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1907/buchner-bio.html |website=www.nobelprize.org |access-date=2016-02-23}}</ref> Buchner demonstrated that the conversion of glucose to ethanol was possible using a non-living extract of yeast, due to the action of [[enzyme]]s in the extract.<ref name = "Cornish-Bowden_1997">{{cite book |publisher=Publicacions de la Universitat de València |title=New Beer in an Old Bottle: Eduard Buchner and the Growth of Biochemical Knowledge | editor-first = Athel | editor-last = Cornish-Bawden |year=1997 |location=Valencia, Spain |chapter=Harden and Young's Discovery of Fructose 1,6-Bisphosphate}}</ref>{{rp|135–148}} This experiment not only revolutionized biochemistry, but also allowed later scientists to analyze this pathway in a more controlled laboratory setting. In a series of experiments (1905–1911), scientists [[Arthur Harden]] and [[William John Young (biochemist)|William Young]] discovered more pieces of glycolysis.<ref name=":1">{{Cite book|title=Bios 302| vauthors = Palmer G |url=http://www.bioc.rice.edu/~graham/Bios302/chapters/Chapter_3.pdf | archive-url = https://web.archive.org/web/20171118060851/http://www.bioc.rice.edu/~graham/Bios302/chapters/Chapter_3.pdf | archive-date = 18 November 2017 |chapter=Chapter 3: The History of Glycolysis: An Example of a Linear Metabolic Pathway. }}</ref> They discovered the regulatory effects of ATP on glucose consumption during alcohol fermentation. They also shed light on the role of one compound as a glycolysis intermediate: fructose 1,6-bisphosphate.<ref name = "Cornish-Bowden_1997" />{{rp|151–158}}

* Firstly, the [[Nicotinamide adenine dinucleotide|NADH + H⁺]] generated by glycolysis has to be transferred to the mitochondrion to be oxidized, and thus to regenerate the NAD⁺ necessary for glycolysis to continue. However the inner mitochondrial membrane is impermeable to NADH and NAD⁺.<ref name=stryer5>{{cite book | vauthors = Stryer L | title = Biochemistry |chapter= Oxidative phosphorylation. |edition= Fourth |location= New York |publisher= W.H. Freeman and Company|date= 1995 |pages= 537–549 |isbn= 0-7167-2009-4 }}</ref> Use is therefore made of two “shuttles”"shuttles" to transport the electrons from NADH across the mitochondrial membrane. They are the [[malate-aspartate shuttle]] and the [[glycerol phosphate shuttle]]. In the former the electrons from NADH are transferred to cytosolic [[Oxaloacetic acid|oxaloacetate]] to form [[Malic acid|malate]]. The malate then traverses the inner mitochondrial membrane into the mitochondrial matrix, where it is reoxidized by NAD⁺ forming intra-mitochondrial oxaloacetate and NADH. The oxaloacetate is then re-cycled to the cytosol via its conversion to aspartate which is readily transported out of the mitochondrion. In the glycerol phosphate shuttle electrons from cytosolic NADH are transferred to [[dihydroxyacetone]] to form [[glycerol-3-phosphate]] which readily traverses the outer mitochondrial membrane. Glycerol-3-phosphate is then reoxidized to dihydroxyacetone, donating its electrons to [[Flavin adenine dinucleotide|FAD]] instead of NAD⁺.<ref name=stryer5 /> This reaction takes place on the inner mitochondrial membrane, allowing FADH₂ to donate its electrons directly to coenzyme Q ([[ubiquinone]]) which is part of the [[electron transport chain]] which ultimately transfers electrons to molecular oxygen {{chem2|O2}}, with the formation of water, and the release of energy eventually captured in the form of [[Adenosine triphosphate|ATP]].

[[Nicotinamide adenine dinucleotide|NAD⁺]] is the oxidizing agent in glycolysis, as it is in most other energy yielding metabolic reactions (e.g. [[beta-oxidation]] of fatty acids, and during the [[citric acid cycle]]). The NADH thus produced is primarily used to ultimately transfer electrons to {{chem2|O2}} to produce water, or, when {{chem2|O2}} is not available, to produce compounds such as [[Lactic acid|lactate]] or [[ethanol]] (see ''Anoxic regeneration of NAD⁺'' above). NADH is rarely used for synthetic processes, the notable exception being gluconeogenesis. During [[Fatty acid metabolism#Fatty acid Synthesis|fatty acid]] and [[Cholesterol#Biosyntesis|cholesterol synthesis]] the reducing agent is [[Nicotinamide adenine dinucleotide phosphate|NADPH]]. This difference exemplifies a general principle that NADPH is consumed during biosynthetic reactions, whereas NADH is generated in energy-yielding reactions.<ref name=stryer0 /> The source of the NADPH is two-fold. When [[Malic acid|malate]] is oxidatively decarboxylated by “NADP"NADP⁺-linked malic enzyme" [[Pyruvic acid|pyruvate]], {{chem2|CO2}} and NADPH are formed. NADPH is also formed by the [[pentose phosphate pathway]] which converts glucose into ribose, which can be used in synthesis of [[nucleotides]] and [[nucleic acids]], or it can be catabolized to pyruvate.<ref name=stryer0 />

In [[combined malonic and methylmalonic aciduria]] (CMAMMA) due to [[ACSF3]] deficiency, glycolysis is reduced by -50%, which is caused by reduced [[Post-translational modification#Cofactors for enhanced enzymatic activity|lipoylation]] of mitochondrial enzymes such as the [[pyruvate dehydrogenase complex]] and [[Oxoglutarate dehydrogenase complex|α-ketoglutarate dehydrogenase complex]].<ref>{{Cite journal |lastlast1=Wehbe |firstfirst1=Zeinab |last2=Behringer |first2=Sidney |last3=Alatibi |first3=Khaled |last4=Watkins |first4=David |last5=Rosenblatt |first5=David |last6=Spiekerkoetter |first6=Ute |last7=Tucci |first7=Sara |date=2019-11-01 |title=The emerging role of the mitochondrial fatty-acid synthase (mtFASII) in the regulation of energy metabolism |url=https://www.sciencedirect.com/science/article/pii/S1388198119301349 |journal=Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids |volume=1864 |issue=11 |pages=1629–1643 |doi=10.1016/j.bbalip.2019.07.012 |pmid=31376476 |issn=1388-1981}}</ref>

This high glycolysis rate has important medical applications, as high [[Aerobic_fermentationAerobic fermentation|aerobic glycolysis]] by malignant tumors is utilized clinically to diagnose and monitor treatment responses of [[cancer]]s by [[Chemical imaging|imaging]] uptake of [[Fluorodeoxyglucose|2-¹⁸F-2-deoxyglucose]] (FDG) (a [[radioactive]] modified hexokinase [[substrate (biochemistry)|substrate]]) with [[positron emission tomography]] (PET).<ref name="pmid11043392">{{cite journal | vauthors = Pauwels EK, Sturm EJ, Bombardieri E, Cleton FJ, Stokkel MP | title = Positron-emission tomography with [18F]fluorodeoxyglucose. Part I. Biochemical uptake mechanism and its implication for clinical studies | journal = Journal of Cancer Research and Clinical Oncology | volume = 126 | issue = 10 | pages = 549–59 | date = October 2000 | pmid = 11043392 | doi = 10.1007/pl00008465 | s2cid = 2725555 }}</ref><ref>{{cite web | title=PET Scan: PET Scan Info Reveals ... | url=http://www.petscaninfo.com/ | access-date=December 5, 2005 }}</ref>

{{wide image|Glycolysis--F-PM.png|1430px|Glycolysis - Structure of anaerobic glycolysis components showed using Fischer projections, left, and polygonal model, right. The compounds correspond to glucose (GLU), glucose 6-phosphate (G6P), fructose 6-phosphate (F6P), fructose 1,6-bisphosphate ( F16BP), dihydroxyacetone phosphate (DHAP), glyceraldehyde 3-phosphate(GA3P), 1,3-bisphosphoglycerate (13BPG), 3-phosphoglycerate (3PG), 2-phosphoglycerate (2PG), phosphoenolpyruvate (PEP), pyruvate (PIR), and lactate (LAC). The enzymes which participate of this pathway are indicated by underlined numbers, and correspond to hexokinase (<u>1</u>), glucose-6-phosphate isomerase (<u>2</u>), phosphofructokinase-1 (<u>3</u>), fructose-bisphosphate aldolase (<u>4</u>), triosephosphate isomerase (<u>5</u>), glyceraldehyde-3-phosphate dehydrogenase (<u>5</u>), phosphoglycerate kinase (<u>7</u>), phosphoglycerate mutase (<u>8</u>), phosphopyruvate hydratase (enolase) (<u>9</u>), pyruvate kinase (<u>10</u>), and lactate dehydrogenase (<u>11</u>). The participant coenzymes (NAD⁺, NADH + H⁺, ATP and ADP), inorganic phosphate, {{chem2|H2O}} and {{chem2|CO2}} were omitted in these representations. The phosphorylation reactions from ATP, as well the ADP phosphorylation reactions in later steps of glycolysis are shown as ~P respectively entering or going out the pathway. The oxireduction reactions using NAD⁺ or NADH are observed as hydrogens “2H”"2H" going out or entering the pathway.}}