<unk>  is the sequence of reactions that converts glucose into pyruvate with the concomitant production of a relatively small amount of ATP. The word is derived from Greek γλυκύς (sweet) and λύσις (letting loose).
It is the initial process of most carbohydrate catabolism, and it serves three principal functions:
As the foundation of both aerobic and anaerobic respiration,<unk>  is the archetype of universal metabolic processes known and occurring (with variations) in many types of cells in nearly all organisms.<unk> , through anaerobic respiration, is the main energy source in many prokaryotes, eukaryotic cells devoid of mitochondria (e.g., mature erythrocytes) and eukaryotic cells under low-oxygen conditions (e.g., heavily-exercising muscle or fermenting yeast).
In eukaryotes and prokaryotes,<unk>  takes place within the cytosol of the cell. In plant cells, some of the glycolytic reactions are also found in the Calvin-Benson cycle, which functions inside the chloroplasts. The wide conservation includes the most phylogenetically deep-rooted extant organisms, and thus it is considered to be one of the most ancient metabolic pathways.
The most common and well-known type of<unk>  is the Embden-Meyerhof pathway, initially explained by Gustav Embden and Otto Meyerhof. The term can be taken to include alternative pathways, such as the Entner-Doudoroff Pathway. However,<unk>  will be used here as a synonym for the Embden-Meyerhof pathway.
The overall reaction of<unk>  is:
The products all have vital cellular uses:
ATP provides an energy source for many cellular functions.
NADH + H+ provides reducing power for other metabolic pathways or further ATP synthesis.
Pyruvate is used in the citric acid cycle in aerobic respiration to produce more ATP, or is converted to other small carbon molecules in anaerobic respiration.
For simple anaerobic fermentations, the metabolism of one molecule of glucose to two molecules of pyruvate has a net yield of two molecules of ATP. Most cells will then carry out further reactions to 'repay' the used NAD+ and produce a final product of ethanol or lactic acid. Many bacteria use inorganic compounds as hydrogen acceptors to regenerate the NAD+.
Cells performing aerobic respiration synthesize much more ATP, but not as part of<unk> . These further aerobic reactions use pyruvate and NADH + H+ from<unk> . Eukaryotic aerobic respiration produces approximately 34 additional molecules of ATP for each glucose molecule, however most of these are produced by a vastly different mechanism to the substrate-level phosphorylation in<unk> .
The lower energy production, per glucose, of anaerobic respiration relative to aerobic respiration, results in greater flux through the pathway under hypoxic (low-oxygen) conditions, unless alternative sources of anerobically-oxidizable substrates, such as fatty acids, are found.
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Glucose
Hexokinase
Glucose 6-phosphate
Glucose-6-phosphateisomerase
Fructose 6-phosphate
phosphofructokinase-1
Fructose 1,6-bisphosphate
Fructose-bisphosphatealdolase
Dihydroxyacetone phosphate
+
Glyceraldehyde 3-phosphate
Triosephosphateisomerase
2 × Glyceraldehyde 3-phosphate
Glyceraldehyde-3-phosphatedehydrogenase
2 × 1,3-Bisphosphoglycerate
Phosphoglycerate kinase
2 × 3-Phosphoglycerate
Phosphoglycerate mutase
2 × 2-Phosphoglycerate
Phosphopyruvatehydratase (Enolase)
2 × Phosphoenolpyruvate
Pyruvate kinase
2 × Pyruvate
Glycolysis
Beta oxidation
Lipogenesis
Pyruvate decarboxylation
Oxidative phosphorylation
Ammonia production
Chiral pool synthesis
Fatty acid metabolism