Ubiquinone ubiquinol produced

Sucdnaterubiquinone Reductase— Reduction of FAD by Succinate to Produce FADH2, Which Ultimately Results in Reduction of Ubiquinone to Produce Ubiquinol for Subsequent Reactions of the Electron Transport Chain... 

Ubiquinone occurs everywhere in living systems, thus giving rise to its name. Its most important role is as a transporter of electrons and energy in the membrane. Ubiquinone is also an antioxidant, as a part of several membrane proteins. One reason for aging of a living system may be sagging supplies of ubiquinone. Ubiquinone is produced in the body and can also be found in many foods. QIO is available as a vitamin for elderly people. Ubiquinone is not fully planar. The structure is not much different from that of the i-system ubiquinol. Furthermore, protons are easily accepted at the oxygen lone pairs. 

This enzyme complex [EC 1.10.2.2], also known as cytochrome bci and complex 111, catalyzes the reaction of ubiquinol (QH2) with two ferricytochrome c to produce ubiquinone (Q) and two ferrocytochrome c. The complex also contains cytochrome h-562, cytochrome h-566, cytochrome Ci, and a two-iron ferredoxin. 

Ubiquinol-10 (reduced form of ubiquinone-10, or coenzyme QIO) is a reactive lipid-soluble antioxidant that may act like ascorbic acid by regenerating vitamin E by reducing the vitamin E radicals produced during lipid peroxidation. 

Complex III (bCj) is docked with ubiquinol (QHj), which is oxidized to ubiquinone (Q) at the site Qo, close to the intermembrane space. Qo delivers one electron to the Fe-S complex and another to cyt Fl. On the matrix side of the membrane, the opposite reaction takes place, but only half the amount can be produced. There is a net delivery of four protons to the intermembrane space, for each two electrons delivered to cyt c. 

The mitochondrial ETC consists of four huge, multieomponent complexes whose function is to transfer electrons from reducing equivalents such as NADH and FADH2, which are produced during glycolysis and the Krebs eyele (Fig. 1). Complex I of the ETC is an NADH dehydrogenase (Fig. 7). Here, NADH is redueed to NAD as it transfers its two electrons to ubiquinone, whieh is oxidized to ubiquinol. Rotenone is a specific inhibitor of complex I. Complex II is a flavoprotein... 

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