Mitchell has explained the concept based on the fact that the reducing equivalents are transferred as H atoms by electron carriers (ubiquinone) and others (such as Fe-S centre and cytochrome). He explained that the hydrogen- and electron-carrying proteins are present in alternate in the respiratory chain to form three functional loops called the oxidation–reduction loops…
The inhibitors involved in the electron transport arrest respiration by combing with membranes of the respiratory chain rather than with the enzymes that are involved in coupling respiration with ATP synthesis. They appear to act at three loci that may be identical to the energy transfer sites I, II, and III as stated in the…
The inhibitors bind to one of the components of ETC and block the transport of electrons. This causes the accumulation of reduced components before the inhibitor blockade step and oxidised components after the inhibitor step. The synthesis of ATP (phosphorylation) depends on electron transport. Hence, all the site-specific inhibitors of ETC also inhibit ATP formation.…
Salient features This is a simpler, radically different, and novel mechanism and was postulated by Peter Mitchell, a British biochemist in 1961. He proposed that “electron transport and ATP synthesis are coupled to high-energy intermediate or an activated protein” as shown in Figure 8.23. According to this model, the transfer of electrons through the respiratory chain…
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…
A beam of ordinary light may be regarded as a bundle of electromagnetic waves vibrating in all directions perpendicular to the axis of the beam. When such a beam of light is made to pass through a specially cut crystal of certain minerals or sheet of special plastic polaroid or a crystal of Iceland spar,…
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…