Question

Discuss the structure and function of the electron transport chain and its
significance on energy production.

Answer 1

Electron transport chain is located in the inner mitochondrial membrane . ETC complexes are oxidized and reduced and thereby transfers proton and electrons across the complexes of ETC. These H+ ions used to produce ATP, the energy currency of the cell. It consists of four complexes -

NADH-Q oxidoreductase - Complex- I

succinate-Q reductase - Complex - II

quinol--cytochrome-c reductase - Complex - III

Cytochrome c oxidase - Complex -IV

Besides these complexes there are two mobile components or ETC also. They are  coenzyme Q (ubiquinone) and cytochrome c.In glycolysis and TCA cycle NADH+H⁺ and FADH₂ are produced which are oxidized by the complexes of ETC. NADH+H⁺ enters the cycle through Complex -I and FADH₂ enters the ETC through complex-II. Each of the complexes moves electrons along a path within its structure formed by a series of fixed, redox-active prosthetic groups. These prosthetic group are   flavin nucleotides (FAD and FMN), quinones, iron-sulfur (Fe-S) clusters, heme, and copper ion. The terminal electron accepter is oxygen atom which is reduced to water.

ETC is coupled with oxidative phosphorylation reaction. When protons are pumped into the inner membrane space, they return to the mitochondrial matrix through ATP synthase enzyme, located at the inner mitochondrial membrane. F0F1 ATPase is responsible for the synthesis of ATP when protons are passed through the protein from inner membrane space to mitochondrial matrix. ATP is the energy currency of the cell and by this oxidative phosphorylation, ATPs are produced.