Oxidative phosphorylation and the electron transport chain

The total oxidation of an organic componnd nsing molecnlar oxygen as the electron acceptor has the potential to yield a very large amonnt of energy, sufficient for the synthesis of several molecnles of ATP from ADP, if there could be one efficiently coupled oxidation process. It is quite unrealistic 

We have already seen the redox reactions of NAD+ and flavoproteins containing FAD or FMN. The 

Ubiquinone is readily reduced to ubiquinol, a process requiring two protons and two electrons similarly, ubiquinol is readily oxidized back to ubiquinone. This redox process is important in oxidative phosphorylation, in that it links hydrogen transfer to electron transfer. The cytochromes are haem-containing proteins (see Box 11.4). As we have seen, haem is an iron-porphyrin complex. Alternate oxidation-reduction of the iron between Fe + (reduced form) and Fe + (oxidized form) in the various cytochromes is responsible for the latter part of the electron transport chain. The individual cytochromes vary structurally, and their classification 

Most compounds oxidized by the electron transport chain donate hydrogen to NAD+, and then NADH is reoxidized in a reaction coupled to reduction of a flavoprotein. During this transformation, sufficient energy is released to enable synthesis of ATP from ADP. The reduced flavoprotein is reoxidized via reduction of coenzyme Q subsequent redox reactions then involve cytochromes and electron transfer processes rather than hydrogen transfer. In two of these cytochrome redox reactions, there is sufficient energy release to allow ATP synthesis. In 

---

These compounds are common in soils and sediments as the products of anaerobic fermentation reactions. Metabolism of these compounds can directly consume O2 (through monooxygenase enzymes) or indirectly, through formation of NADH which is shuttled into oxidative phosphorylation and the electron transport chain. Oxidative metabolism of Ci compounds is an important microbial process in soils and sediments, consuming the methane produced by methanogenesis. 

---