Glycolysis system

Article

January 18, 2022

Glycolysis (Glycolysis) is the name of the biochemical reaction pathway that exists in the body. It decomposes (catabolizes) glucose into organic acids such as pyruvic acid and has high bonds contained in glucose. It is a metabolic process for converting energy into a form that is easy for living organisms to use. Almost all organisms have glycolysis and are considered to be the most primitive metabolic system. While it is a typical metabolic system that can occur even in an anaerobic state (respiratory state, anoxic state), it is favorable because the reducing power and pyruvic acid obtained are passed to the electron transport chain and citric acid cycle. It also functions as part of air breathing.

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There are several types of glycolysis. Emden-Meyerhof route (EM route) Entner-Dudlov route (ED route) The pentose phosphate pathway (PP pathway) The most common of these is the Emden-Meyerhoff pathway, which is used by all of our well-known eukaryotes and anaerobic eubacteria. The Entner-Dudlov pathway is common in aerobic eubacteria. The pentose phosphate pathway may not be included in glycolysis for that purpose. In archaea, the modified EM pathway and the modified ED pathway, which are different in detail from those described below, are selected by individual species. The Emden-Meyerhoff route is also called the Emden-Meierhoff-Parnas route (EMP route).

Emden-Meyerhof route

The Emden-Meyerhoff pathway (hereinafter referred to as the EM pathway) is a glucose metabolism system of eukaryotes and anaerobic eubacteria. The EM pathway involves more than a dozen enzymes, and it is possible to produce ATP, which is an energy currency, even in anoxic conditions. In aerobic organisms, it is used as the first stage of aerobic respiration, in which case the reaction proceeds to pyruvic acid, from which it enters the citric acid cycle. Conversely, in anoxic conditions, pyruvic acid changes to organic acids such as lactic acid and ethanol. This is to supplement the NAD + etc. required to continue the EM circuit by reducing pyruvic acid to lactic acid. The fermentation process occurs in this glycolytic system (lactic acid fermentation, ethanol fermentation, etc.). In addition, even in aerobic organisms, when ATP that exceeds the capacity of the citric acid cycle is required due to excessive exercise, ATP synthesis by glycolysis becomes active and pyruvic acid that cannot be processed by the citric acid cycle is generated. As a result, the blood lactic acid concentration increases because excess pyruvic acid is converted to lactic acid. It has long been believed that the accumulation of lactic acid in muscle fibers is the cause of post-exercise muscle soreness, but in recent years the idea that minute damage to muscle fibers is the main cause of muscle soreness has become mainstream. (See Lactic Acid on English Wikipedia). Regarding the balance of ATP, although 4 molecules of ATP are produced in the reaction, 2 molecules of ATP are consumed due to phosphorylation of glucose and fructose 6-phosphate, so 2 molecules of ATP per molecule of glucose are convenient. Will be generated. In addition, NADH used in the electron transport chain produces two molecules. Deformed EM pathway A metabolic system similar to the EM pathway used by some archaea (Thermococci and Methanococci, both anaerobic Euryarchaeota). The major difference is that the pathway from glyceraldehyde 3-phosphate to phosphoglyceric acid is bypassed compared to the EM pathway. For this reason, ATP originally produced in this system is not produced, but phos

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