Electron transport chain of mitochondria

Abstract The supramolecular composites containing fullerenes C60 immobilized at nanosilica were used for the design of the molecular systems that can be an effective agent in cancer photodynamic therapy (PDT). In particular, it was shown that photoexcited fullerene C60-containing composites decrease viability of transformed cells, intensify the process of lipid peroxidation (LPO) in cell membranes and accumulation of low-molecular weight DNA fragments, and also decrease the activity of electron-transport chain of mitochondria. 

From the data of literature it is known that water-soluble derivatives of fullerenes are able to be localized in mitochondria and influence their state as well as enzyme system (Foley et al., 2002). Such intracellular localization of fullerenes C60 could explain biologic effects under irradiation, because generation of free oxygen radicals in the cells occurs during emission of electrons from electron-transport chain of mitochondria. 

The transport of electrons generated in catabolic pathways down the electron transport chain of mitochondria results in the production of essential quantities of ATP. 

Figure 1 7.3 The electron transport chain of mitochondria and the coupling of electron transfer reactions to the creation of a proton concentration gradient across the inner mitochondrial membrane. This proton concentration gradient is ultimately employed to drive the synthesis of ATP by ATP synthase, noted here as complex V. (Reproduced from D. Voet and J. G Voet, Biochemistry, 3rd edn, 2004 2004, Donald and Judith G. Voet. Reprinted with permission of John Wiley and Sons, Inc.)...

Figure 10-5 An abbreviated version of the electron transport chain of mitochondria. Four electrons reduce 02 to 2 H20. For details see Figs. 18-5 and 18-6.

Three facts account for the need of cells for both the flavin and pyridine nucleotide coenzymes (1) Flavins are usually stronger oxidizing agents than is NAD+. This property fits them for a role in the electron transport chains of mitochondria where a sequence of increasingly more powerful oxidants is needed and makes them ideal oxidants in a variety of other dehydrogenations. (2) Flavins can be reduced either by one- or two-electron processes. This enables them to participate in oxidation reactions involving free radicals and in reactions with metal ions. (3) Reduced flavins... 

Figure 18-5 A current concept of the electron transport chain of mitochondria. Complexes I, III, and IV pass electrons from NADH or NADPH to 02, one NADH or two electrons reducing one O to HzO. This electron transport is coupled to the transfer of about 12 H+ from the mitochondrial matrix to the intermembrane space. These protons flow back into the matrix through ATP synthase (V), four H+ driving the synthesis of one ATP. Succinate, fatty acyl-CoA molecules, and other substrates are oxidized via complex II and similar complexes that reduce ubiquinone Q, the reduced form QH2 carrying electrons to complex III. In some tissues of some organisms, glycerol phosphate is dehydrogenated by a complex that is accessible from the intermembrane space.

Figure 17.4 The electron transport chain of mitochondria. Triangles indicate sites of inhibition by various compounds. Cyt, cytochrome ETF, electron transfer flavoprotein. (Reproduced with permission from Moreadith RW, Batshaw ML, Ohnishi T, Kerr D, Knox B, Jackson D, Hruben R, Olson J, Reynafarje B, Lehninger AL. Deficiency of the iron-sulfur clusters of mitochondrial reduced nicotinamide-adenine dinucleotide-ubiquinone oxidoreductase (complex I) in an infant with congenital lactic acidosis J Clin Invest 74 685-697, 1984.)...

The Q cycle plays a major role in the electron transport chain of mitochondria, chloroplasts, and bacteria. What is the function of the Q cycle, and how does it carry out this function What electron transport train components participate in the Q cycle in mitochondria, in purple bacteria, and in chloroplasts ... 

Measure States of Oxidation of Carriers in the Electron Transport Chain of Mitochondria... 

The electron transport chains of mitochondria and chloroplasts are similar. In mitochondria, antimycin A inhibits electron transfer from cytochrome b to coenzyme Q in the Q cycle. By analogy, it can be argued that antimycin A inhibits electron flow from plastoquinone to cytochrome b-f. A Q cycle may also operate in chloroplasts. 

Figure 8.8. Stereo view of E. coli succinate ubiquinone oxidoreductase, which is an analogue of Complex II of the electron transport chain of mitochondria, with neutral residues light gray, aromatics black, other hydrophobics gray, and charged residues white. (A) Space-filling representation with water...

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