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ETS or electron transport system is locatedin the inner mitochondrial membrane. It helps in releasing and utilizing the energystored in NADH+H+ and FADH2. NADH+ H+, which is formed during glycolysis and citric acidcycle, gets oxidized by NADH dehydrogenase (complex I). The electrons so generatedget transferred to ubiquinone through FMN. In a similar manner, FADH2 (complex II) generated during citric acidcycle gets transferred to ubiquinone. The electrons from ubiquinone arereceived by cytochrome bc1 (complex III) and further get transferredto cytochrome c. The cytochrome c acts as a mobile carrier between complex III andcytochrome c oxidase complex, containing cytochrome a and a3, along with copper centres (complex IV).
During the transfer of electrons from each complex, theprocess is accompanied by the production of ATP from ADP and inorganicphosphate by the action ATP synthase (complex V). The amount of ATP produceddepends on the molecule, which has been oxidized. 2 ATP molecules are producedby the oxidation of one molecule of NADH. One molecule of FADH2, on oxidation, gives 3 ATP molecules.