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The ATP generated in this process is made by substrate-level phosphorylation, which does not require oxygen. Fermentation is less efficient at using the energy from glucose: only 2 ATP are produced per glucose, compared to the 38 ATP per glucose nominally produced by aerobic respiration. Glycolytic ATP, however, is produced more quickly.
Relative contribution of ATP production of bioenergetic systems during aerobic exercise at maximum intensity (e.g. sprinting) Aerobic and anaerobic systems usually work concurrently. When describing activity, it is not a question of which energy system is working, but which predominates. [1] [8]
Anaerobic cellular respiration and fermentation generate ATP in very different ways, and the terms should not be treated as synonyms. Cellular respiration (both aerobic and anaerobic) uses highly reduced chemical compounds such as NADH and FADH 2 (for example produced during glycolysis and the citric acid cycle) to establish an electrochemical gradient (often a proton gradient) across a membrane.
Glycolysis can be either an aerobic or anaerobic process. When oxygen is present, glycolysis continues along the aerobic respiration pathway. If oxygen is not present, then ATP production is restricted to anaerobic respiration. The location where glycolysis, aerobic or anaerobic, occurs is in the cytosol of the cell.
Anaerobic respiration is correspondingly less efficient than aerobic respiration. In the absence of oxygen, not all of the carbon-carbon bonds in glucose can be broken to release energy. A great deal of extractable energy is left in the waste products. Anaerobic respiration generally occurs in prokaryotes in environments that do not contain oxygen.
The energy yield of anaerobic respiration and fermentation (i.e. the number of ATP molecules generated) is less than in aerobic respiration. [8] This is why facultative anaerobes, which can metabolise energy both aerobically and anaerobically, preferentially metabolise energy aerobically.
The anaerobic glycolysis (lactic acid) system is dominant from about 10–30 seconds during a maximal effort. It produces 2 ATP molecules per glucose molecule, [3] or about 5% of glucose's energy potential (38 ATP molecules). [4] [5] The speed at which ATP is produced is about 100 times that of oxidative phosphorylation. [1]
An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenated environment.