Answer to Question #97120 in Cell Biology for Abhishek

Question

Briefly explain the mechanism of formation of proton gradient in mitochondria .

Answer 1

The electron transport chain is a system of transmembrane proteins and electron carriers that maintain the energy balance of the cell. ETC maintains balance due to the transfer of electrons and protons from NADH and FADH₂ to the electron acceptor O₂. The energy released in the electron transfer process through the respiratory chain is stored in the form of an electrochemical proton gradient at the inner mitochondrial membrane. Respiratory enzyme complexes combine electron transport, accompanied by the release of energy, with the pumping of protons from the mitochondria matrix. Complex I (NADH-CoQ-oxidoreductase) receives electrons from NADH, transfers them to coenzyme Q (ubiquinone), and also moves four proton ions to the outer surface of the inner mitochondrial membrane. In complex III, the Q-cycle is responsible for the transfer of protons, whereas, in cytochrome c-oxidase (complex IV), H⁺ transport is coupled to the electron flux from cytochrome C to O₂.