Question

Explain ETS.

Answer 1

ETS or electron transport system is located in the inner mitochondrial membrane. It helps in releasing and utilising the energy stored in NADH and FADH2. NADH, which is formed during glycolysis and citric acid cycle, is oxidised by NADH dehydrogenase (Complex I). The electrons released are transferred to ubiquinone through FMN.

In a similar manner, FADH2 formed during the citric acid cycle donates electrons through succinate dehydrogenase (Complex II) to ubiquinone. The electrons from ubiquinone are then transferred to cytochrome bc1 complex (Complex III) and further passed on to cytochrome c.

Cytochrome c acts as a mobile electron carrier between Complex III and cytochrome c oxidase complex (Complex IV), which contains cytochrome a and a3 along with copper centres. Oxygen acts as the final electron acceptor and combines with electrons and protons to form water.

During the transfer of electrons through the electron transport chain, energy is released and used for the synthesis of ATP from ADP and inorganic phosphate by ATP synthase (Complex V). The amount of ATP produced depends on the molecule oxidised. Oxidation of one molecule of NADH produces two ATP molecules, while oxidation of one molecule of FADH2 produces three ATP molecules.