Oxidative Phosphorylation

Oxidative phosphorylation is a cellular process that harnesses the reduction of oxygen to generate high-energy phosphate bonds in the form of adenosine triphosphate (ATP). It is a series of oxidation-reduction reactions that involve the transfer electrons from NADH and FADH2 to oxygen across several protein, metal, and lipid complexes in the mitochondria known as the electron transport chain (ETC). The electron transport chain utilizes NADH and FADH2 generated from several catabolic cellular processes. Also, oxidative phosphorylation utilizes elemental oxygen as the final oxidizing agent (and electron acceptor). Mitochondrial function and the electron transport chain shed light on the evolution and advancement of aerobic eukaryotic life, especially when compared to anaerobic organisms. It is the hallmark of aerobic respiration and is the reason why a plethora of lifeforms require oxygen to survive.
Most of the usable energy obtained from the breakdown of carbohydrates or fats is derived by oxidative phosphorylation, which takes place within mitochondria. For example, the breakdown of glucose by glycolysis and the citric acid cycle yields a total of four molecules of ATP, ten molecules of NADH, and two molecules of FADH2. Electrons from NADH and FADH2 are then transferred to molecular oxygen, coupled to the formation of an additional 32 to 34 ATP molecules by oxidative phosphorylation. Electron transport and oxidative phosphorylation are critical activities of protein complexes in the inner mitochondrial membrane, which ultimately serve as the major source of cellular energy^[1][2].

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