Question

What happens to an electron during the electron transport chain (ETC)? Where does the electron end up at the end of the ETC?

Answer 1

The metabolic pathway through which  the electron passes from one carrier to another is called the electron transport chain.It is present in the inner mitochondrial membrane.Electrons from NADH produced in the mitochondrial matrix during citric acid cycle are oxidised by an NADH dehydrogenase(complex I),electrons are then transferred to ubiquinone located within the inner membrane .Ubiquinone also receives reducing equivalents via FADH2(complex II) that is geberated during oxidation of succinate in the citric acid cycle.The reduced ubiquinone (ubiquinol) is then oxidised with the transfer of electrons to cytochrome c via cytochrome bc1 complex(complex III).cyctochrome c acts as a mobile carrier for transfer of electrons between complex III and IV.When the electrons passed from one carrier to another Via  complex I to IV in the electron transport chain ,they are coupled to ATP synthase (complex V) for the production of ATP from ADP and inorganic phosphate.The electrons as they move through the system release enough energy that are trapped to synthesise ATP.

At the end of ETC ,electron end up by oxygen. Although the aerobic cycle process of respiration takes place only in the presence of oxygen,the role of oxygen is limited to the terminal stage of the process.oxygen drives the whole process by removing hydrogen from the system.Oxygen acts as final hydrogen acceptor.oxygen is the ultimate acceptor of electrons and it gets reduced to water .