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Fermentation, oxidative phosphorylation, and aerobic respiration are three terms related to the process of cellular respiration, which is how cells break down glucose and other organic molecules to produce energy in the form of ATP.
Fermentation is an anaerobic process, meaning it does not require oxygen. It consists of glycolysis, which splits glucose into two molecules of pyruvate, and a series of reactions that convert pyruvate into other compounds and regenerate NAD+, which is needed for glycolysis to continue. Fermentation produces a net of 2 ATP per glucose molecule. Different organisms use different types of fermentation, such as lactic acid fermentation in animal cells and alcoholic fermentation in yeast cells.
Oxidative phosphorylation is the final stage of aerobic respiration, meaning it requires oxygen. It involves the electron transport chain and chemiosmosis, which are processes that use the energy from electrons donated by NADH and FADH2 (products of glycolysis and the Krebs cycle) to pump protons across the inner mitochondrial membrane and create a proton gradient. The protons then flow back through ATP synthase, a protein complex that uses the proton motive force to generate ATP. Oxidative phosphorylation produces about 34 ATP per glucose molecule.
Aerobic respiration is the overall process of breaking down glucose in the presence of oxygen to produce carbon dioxide, water, and ATP. It has three main stages: glycolysis, which occurs in the cytoplasm and produces 2 ATP and 2 NADH; the Krebs cycle, which occurs in the mitochondrial matrix and produces 2 ATP, 6 NADH, and 2 FADH2; and oxidative phosphorylation, which occurs in the inner mitochondrial membrane and produces about 34 ATP. Aerobic respiration is more efficient than fermentation because it can extract more energy from glucose by using oxygen as the final electron acceptor.
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