Copyright © Philip M. Parker, INSEAD. Terms of Use.
Definition: Glycolysis |
GlycolysisNoun1. A metabolic process that breaks down carbohydrates and sugars through a series of reactions to either pyruvic acid or lactic acid and release energy for the body in the form of ATP. Source: WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved. |
| Domain | Definition |
Chemistry | The energy yielding conversion of glucose to lactic acid in various tissues, notably muscle; since molecular oxygen is not consumed in this process it is often referred to as "anaerobic G" Source: European Union. (references) |
Health | The pathway by which glucose is catabolized into two molecules of pyruvic acid with the generation of ATP. (references) |
Source: compiled by the editor from various references; see credits. | |
(From Wikipedia, the free Encyclopedia)
Glycolysis (from Greek glyk meaning sweet and lysis meaning dissolving) is the inital stage of glucose metabolism. The most common and well-known form of glycolysis is the Embden-Meyerhof pathway. The term can be taken to include alternative pathways, such as the Entner-Doudoroff pathway. However, glycolysis will be used here as a synonym for the Embden-Meyerhof pathway.Glycolysis converts 1 molecule of glucose into 2 molecules of pyruvate, along with "reducing equivalents" in the form of NADH. Glycolysis proper is completely anerobic; that is, oxygen is not required. In eukaryotes it takes place within the cytosol of the cell (as opposed to the mitochondria, where reactions more closely connected to aerobic metabolism occur).
The ultimate fate of the pyruvate and NADH produced in glycolysis depends upon the organism and the conditions, most notably the presence or absence of oxygen or other external electron acceptors. In fermentation, the pyruvate and NADH are anerobically metabolized to yield any of a variety of products. For example, the bacteria involved in making yogurt simply reduce the pyruvate to lactic acid, whereas yeast produce ethanol and carbon dioxide. In aerobic organisms, the pyruvate typically enters the citric acid cycle, and the NADH is ultimately oxidized by oxygen. Although human metabolism is primarily aerobic, under anerobic conditions, for example in over-worked muscles that are starved for oxygen, pyruvate is converted to lactate, as in many microorganisms.
Glycolysis is the only metabolic pathway common to nearly all living organisms, suggesting great antiquity; it may have originated with the first prokaryotes, 3.5 billion years ago or more.
The first step in glycolysis is phosphorylation of glucose by hexokinase (in liver the enzyme is glucokinase which has slightly different properties). This reaction consumes 1 ATP molecule, but the energy is well spent: although the cell membrane is freely permeable to glucose because of the presence of glucose transport proteins, it is impermeable to glucose 6-phosphate. Glucose 6-phosphate is then rearranged into fructose 6-phosphate by phosphoglucose isomerase. (Fructose can also enter the glycolytic pathway at this point.)
Phosphofructokinase-1 then consumes 1 ATP to form fructose 1,6-bisphosphate. The energy expenditure in this step is justified in 2 ways: the glycolytic process (up to this step) is now irreversible, and the energy supplied to the molecule allows the ring to be split by aldolase into 2 molecules - dihydroxyacetone phosphate and glyceraldehyde 3-phosphate. (Triosephosphate isomerase converts the molecule of dihydroxyacetone phosphate into a molecule of glyceraldehyde 3-phosphate.) Each molecule of glyceraldehyde 3-phosphate is then oxidized by a molecule of NAD+ in the presence of glyceraldehyde 3-phosphate dehydrogenase, forming 1,3-bisphosphoglycerate.
In the next step, phosphoglycerate kinase generates a molecule of ATP while forming 3-phosphoglycerate. At this step glycolysis has reached the break-even point: 2 molecules of ATP were consumed, and 2 new molecules have been synthesized. This step, one of the two substrate-level phosphorylation steps, requires ADP; thus, when the cell has plenty of ATP (and little ADP) this reaction does not occur. Because ATP decays relatively quickly when it is not metabolized, this is an important regulatory point in the glycolytic pathway. Phosphoglyceromutase then forms 2-phosphoglycerate; enolase then forms phosphoenolpyruvate; and another substrate-level phosphorylation then forms a molecule of pyruvate and a molecule of ATP. This serves as an additional regulatory step.
After the formation of fructose 1,6 bisphosphate, many of the reactions are energetically unfavorable. The only reactions that are favorable are the 2 substrate-level phosphorylation steps that result in the formation of ATP. These two reactions pull the glycolytic pathway to completion.
So, for simple fermentations, the metabolism of 1 molecule of glucose has a net yield of 2 molecules of ATP. Cells performing respiration synthesize much more ATP. Eukaryotic aerobic respiration produces an additional 34 molecules (approximately) of ATP for each glucose molecule oxidized.
- See also: Gluconeogenesis
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Glycolysis."
Crosswords: Glycolysis |
| English words defined with "glycolysis": zymase. (references) |
| Specialty definitions using "glycolysis": Acetate Kinase ♦ Buformin ♦ Dihydroxyacetone Phosphate ♦ fructose-1,6-biphosphate aldolase, Fructosediphosphates ♦ glucokinase, Glyceraldehyde 3-Phosphate, Glyceraldehyde-3-Phosphate Dehydrogenases ♦ Mannose-6-Phosphate Isomerase ♦ Pyruvate Metabolism, Inborn Errors ♦ Substrate Cycling. (references) |
| Domain | Title |
Books | |
Source: compiled by the editor from various references; see credits. | |
| "Glycolysis" is generally used as a noun (singular) -- approximately 100.00% of the time. "Glycolysis" is used about 8 times out of a sample of 100 million words spoken or written in English. Its rank is based on over 700,000 words used in the English language. Some parts-of-speech are not covered due to the samples used by the British National Corpus. (note: percents less than one-hundredth of one percent have been omitted) |
| Parts of Speech | Percent | Usage per 100 Million Words | Rank in English |
| Noun (singular) | 100% | 8 | 124,375 |
Source: compiled by the editor from several corpora; see credits.
| The following statistics estimate the number of searches per day across the major English-language search engines as identified by various trade publications. Hyperlinks lead to commercial use of the expression at Amazon.com. |
| Expression | Frequency per Day |
glycolysis | 131 |
cycle glycolysis krebs | 5 |
glycolysis summary | 4 |
glycolysis pathway | 4 |
anaerobic glycolysis | 3 |
diagram glycolysis | 3 |
aerobic glycolysis | 2 |
glycolysis yeast | 2 |
glycolysis reaction | 2 |
definition glycolysis | 2 |
glycolysis product | 2 |
| Source: compiled by the editor from various references; see credits. | |
| Language | Translations for "glycolysis"; alternative meanings/domain in parentheses. | |
Danish | glykolyse (glycogenesis, glycogenolysis), glykogenolyse (glycogenesis, glycogenolysis), glycolyse (glycogenesis, glycogenolysis), glukogenese (glycogenesis, glycogenolysis). (various references) | |
Dutch | glycolyse (glycogenesis, glycogenolysis), glycogenesis (glycogenesis, glycogenolysis), glycogenese (glycogenesis, glycogenolysis), glucogenesis (glycogenesis, glycogenolysis), glucogenese (glycogenesis, glycogenolysis). (various references) | |
Finnish | glykolyysi (glycogenesis, glycogenolysis), glykogenolyysi (glycogenesis, glycogenolysis). (various references) | |
French | glycolyse (glycogenesis, glycogenolysis), glycogénolyse (glycogenesis, glycogenolysis), glycogénèse (glycogenesis, glycogenolysis). (various references) | |
German | Glykolyse (EM pathway, Embden-Meyerhof glycolytic pathway, Embden-Meyerhof pathway, Embden-Meyerhof pathway glycolysis, glycogenesis, glycogenolysis), Glukogenie (glycogenesis, glycogenolysis), Glukogenese (glycogenesis, glycogenolysis). (various references) | |
Greek | αναερόβια γλυκόλυση (EM pathway, Embden-Meyerhof glycolytic pathway, Embden-Meyerhof pathway, Embden-Meyerhof pathway glycolysis), οδός Embden-Meyerhof (EM pathway, Embden-Meyerhof glycolytic pathway, Embden-Meyerhof pathway, Embden-Meyerhof pathway glycolysis). (various references) | |
Italian | glicolisi (glycogenesis, glycogenolysis), glicogenesi (glycogenesis, glycogenolysis). (various references) | |
Japanese Kanji | 解糖 . (various references) | |
Japanese Katakana | かいとう (answer, dissolution, good pitch, mysteriousthief, reply, sharp sword, society president, solution, thaw). (various references) | |
Pig Latin | ycolysisglay.(various references) | |
Portuguese | glicogenólise (glycogenesis, glycogenolysis), glicogénese (glycogenesis, glycogenolysis), glicólise (glycogenesis, glycogenolysis). (various references) | |
Spanish | glucosis (glycogenesis, glycogenolysis), glucogénesis (glycogenesis, glycogenolysis), glicogénesis (glycogenesis, glycogenolysis). (various references) | |
Swedish | glykolys (glycogenesis, glycogenolysis). (various references) | |
| Source: compiled by the editor from various translation references. | ||
Scrabble® Enable2K-Verified Anagrams | |
| Words within the letters "c-g-i-l-l-o-s-s-y-y" | |
-1 letter: glycosyls. | |
-2 letters: glossily, glycosyl. | |
-3 letters: glycols, glycyls. | |
-4 letters: cosily, glossy, glycol, glycyl, logics, logily, siglos. | |
-5 letters: cissy, clogs, cloys, coils, colly, coyly, gills, gilly, gloss, golly, logic, lossy, lysis, sills, silly, silos, slily, slogs, slyly, soils, sylis, yills, yogic, yogis. | |
| Words containing the letters "c-g-i-l-l-o-s-s-y-y" | |
+4 letters: glycogenolysis, glycosylations. | |
+5 letters: dyslogistically, syllogistically. | |
| Source: compiled by the editor from various references; see credits. SCRABBLE® is a registered trademark. All intellectual property rights in and to the game are owned in the U.S.A and Canada by Hasbro Inc., and throughout the rest of the world by J.W. Spear & Sons Limited of Maidenhead, Berkshire, England, a subsidiary of Mattel Inc. Mattel and Spear are not affiliated with Hasbro. | |
Copyright © Philip M. Parker, INSEAD. Terms of Use.
