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Importantly, under low-oxygen (anaerobic) conditions, glycolysis is the only biochemical pathway in eukaryotes that can generate ATP, and, for many anaerobic respiring organisms the most important producer of ATP. [7] Therefore, many organisms have evolved fermentation pathways to recycle NAD + to
This potential is then used to drive ATP synthase and produce ATP from ADP and a phosphate group. Biology textbooks often state that 38 ATP molecules can be made per oxidized glucose molecule during cellular respiration (2 from glycolysis, 2 from the Krebs cycle, and about 34 from the electron transport system). [5]
Though slower than glucose, its yield is much higher. One molecule of glucose produces through aerobic glycolysis a net of 30-32 ATP; [11] whereas a fatty acid can produce through beta oxidation a net of approximately 100 ATP depending on the type of fatty acid. For example, palmitic acid can produce a net of 106 ATP. [12]
Substrate-level phosphorylation exemplified with the conversion of ADP to ATP. Substrate-level phosphorylation is a metabolism reaction that results in the production of ATP or GTP supported by the energy released from another high-energy bond that leads to phosphorylation of ADP or GDP to ATP or GTP (note that the reaction catalyzed by creatine kinase is not considered as "substrate-level ...
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]
Oxidative phosphorylation contributes the majority of the ATP produced, compared to glycolysis and the Krebs cycle. While the ATP count is glycolysis and the Krebs cycle is two ATP molecules, the electron transport chain contributes, at most, twenty-eight ATP molecules. A contributing factor is due to the energy potentials of NADH and FADH 2.
Compare this to the glycerol 3-phosphate shuttle, which reduces FAD + to produce FADH 2, donates electrons to the quinone pool in the electron transport chain, and is capable of generating only 2 ATPs per NADH generated in glycolysis (ultimately resulting in a net gain of 36 ATPs per glucose metabolized).
Phosphorylation initiates the reaction in step 1 of the preparatory step [5] (first half of glycolysis), and initiates step 6 of payoff phase (second phase of glycolysis). [ 6 ] Glucose, by nature, is a small molecule with the ability to diffuse in and out of the cell.