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Carbohydrate catabolism is the breakdown of carbohydrates to yield an energy rich compound called ATP. The production of ATP is achieved through the oxidation of glucose molecules. In oxidation, the electrons are stripped from a glucose molecule to reduce NAD+ and FAD. NAD+ and FAD possess a high energy potential to drive the production of ATP in the electron transport chain. ATP production occurs in the mitochondria of the cell. There are two methods of producing ATP: aerobic and anaerobic. In aerobic respiration, oxygen is required. Oxygen plays a key role as it increases ATP production from 4 ATP molecules to about 30 ATP molecules. In anaerobic respiration, oxygen is not required. When oxygen is absent, the generation of ATP continues through fermentation.There are two types of fermentation: alcohol fermentation and lactic acid fermentation. There are several different types of carbohydrates: polysaccharides (e.g., starch, amylopectin, glycogen, cellulose), monosaccharides (e.g., glucose, galactose, fructose, ribose) and the disaccharides (e.g., sucrose, maltose, lactose). Glucose reacts with oxygen in the following redox reaction, C6H12O6 + 6O2 → 6CO2 + 6H2O, Carbon dioxide and water are waste products, and the overall reaction is exothermic. The breakdown of glucose into energy in the form of molecules of ATP is therefore one of the most important biochemical pathways found in living organisms. ==Glycolysis== (詳細はGlycolysis, which means “sugar splitting,” is the initial process in the cellular respiration pathway. Glycolysis can be either an aerobic or anaerobic process. When oxygen is present then glycolysis will continue along the aerobic respiration pathway. If oxygen is not present, then ATP production will be restricted to anaerobic respiration. The location where glycolysis, aerobic or anaerobic, occurs is in the cytosol of the cell. In glycolysis, a six-carbon glucose molecule is split into two three-carbon molecules called pyruvate. These carbon molecules are oxidized into NADH and ATP. In order for the glucose molecule to be oxidized into pyruvate, an input of ATP molecules is required. This is known as the investment phase, in which a total of two ATP molecules are consumed. At the end of glycolysis, the total yield of ATP is four molecules, but the net gain is two ATP molecules. Even though ATP is synthesized, the two ATP molecules produced are few compared to the second and third pathways, Krebs cycle and oxidative phosphorylation. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Carbohydrate catabolism」の詳細全文を読む スポンサード リンク
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