In mitochondria that are actively phosphorylating in the presence of an excess of ADP, the inner membrane pulls way from the outer membrane and assumes a condensed state. In the absence of ADP, the mitochondria have the normal structure or the swollen state, in which the cristae project into the large matrix. According to this…

This is the most accepted of the three hypotheses and proposes that electron transport is coupled to ATP synthesis by a sequence of consecutive reactions, in which a high energy covalent intermediate is formed by the electron transport and subsequently is cleaved and donates its energy to form ATP. The hypothesis explains the direct chemical coupling…

Three principal hypotheses have been advanced to account for the coupling of oxidation and phosphorylation. In other words, these hypotheses explain how the energy transfer between electron transport and ATP synthesis takes place.

Rotational catalysis a key to the binding change mechanism for ATP synthesis. Paul Boyer proposed a mechanism in which the three active sites of F1 take turns in the catalysis of ATP synthesis. A given β subunits start in the β-ADP conformation, which binds ADP and Pi from the surrounding medium. The subunit now changes conformation,…

Mitochondrial ATP synthase is an F-type ATPase. It catalyses the formation of ATP and Pi accompanied to the flow of protons from the P to N side of the membrane. ATP synthase also called complex V has two distinct components: F1 – a peripheral membrane protein F0 – integral to the membrane, and 0 stands for oligomycin…

Complex IV is also known as cytochrome oxidase and contains cytochromes a and a3 as shown in Figure 8.19. The cytochromes are made up of two heme groups bound to different regions of the same large protein, which are therefore functionally and spectrally different. In addition, complex IV contains two copper ions, CuA and CuB, which are…

This is also called cytochrome bc1 complex or ubiquinone, cytochrome-oxidoreductase. This couples the transfer of electrons from ubiquinol (QH2) to cytochrome c with the vectorial transport of protons from the matrix to the intermembrane space. Net equation for the redox reactions of Q cycle:   QH2 + 2Cyt c1 (oxidised) + 2H + N → Q…

Complex II is called succinate dehydrogenase complex. It is the only membrane-bound enzyme in TCA. Complex II is smaller and simpler than complex I. However, it contains two types of prosthetic groups and at least four different proteins. To the first protein FAD is covalently bound and Fe-S centre with four Fe atoms. In addition,…

Helmut Beinert first discovered that the iron is present in heme and associated with inorganic sulphur atoms or with sulphur atoms of cysteine residues in the proteins or both. These iron sulphur (Fe-S) centres range from simple structures with single Fe atom coordinated with four cys-SH groups to more complex Fe-S centres with two or…

ELECTRON CARRIERS Electron carriers in the electron transport chain are the following: