Electron transport components

Pretreatment with the Type I substrate, ethylmorphine, resulted in 100% mortality in both rats and mice, and aminopyrine pretreatment resulted in 100% and 64% mortality in rats and mice, respectively, exposed to disulfoton (Pawar and Fawade 1978). Nickel chloride, cobalt chloride, or cycloheximide decreased the levels of cytochrome bs, cytochrome c reductase, and total heme in rats (Fawade and Pawar 1983). These electron transport components were further decreased in rats pretreated with these inhibitors and given a single dose of disulfoton. Data from this study suggests an additive effect, since disulfoton also decreases the activities of these components. Evidence of an additive effect between disulfoton and these metabolic inhibitors was suggested by the decrease in ethylmorphine N-demethylase and acetanilide hydroxylase activities when rats were given an inhibitor followed by disulfoton. In another experiment, these inhibitors decreased the activity of delta-aminolevulinic acid synthetase, but this decrease was reversed when disulfoton was administered. 

Ellis JE, William R, Cole D, et al. 1993. Electron-transport components of the parasitic protozoan Giardia lamblia. Febs Lett 325 196-200. 

Ellis JE, Williams R, Cole D, Cammack R, Lloyd D (1993) Electron transport components of the parasitic protozoon Giardia lamblia. FEBS Lett 325 196-200 Embley TM, Finlay BJ, Dyal PL, Hirt RP, Wilkinson M, Williams AG (1995) Multiple origins of anaerobic abates with hydrogenosomes within the radiation of aerobic abates. Proc R Soc Lond Biol Sci 262 87-93... 

Correct answer = D. Thirteen of the approximately 100 polypeptides required for oxidative phosphorylation are coded for by mitochondrial DNA, including the electron transport components cytochrome c and coenzyme Q. Oxygen directly oxidizes cytochrome oxidase. Succinate dehydrogenase directly reduces FAD. Cyanide inhibits electron flow, proton pumping, and ATP synthesis. 

In higher plants and animals, electron transport occurs within the mitochondria. Biochemists have devised methods to isolate intact mitochondria containing all of the functional citric-acid-cycle enzymes and electron-transport components. Such in-... 

Ghiorse, W. C. Ehrlich, H. L. (1976). Electron transport components of the Mn02... 

Protohemin is the major structural component of the active site, and, indeed, is the principal determinant of activity and specificity in hemopro-teins. While hemoproteins are generally categorized into the three classes of oxidases, peroxidases, and electron transport components, the first two groups may have a number of features in common in that the oxidase activity may involve certain steps in which peroxide compounds are involved, and the peroxidases may participate in oxidase activities under appropriate conditions. Nevertheless, it is the purpose of this contribution to explore how the apoenzyme determines the fine structure of the catalytic activities of the hemoprotein 71). In this context, two hypotheses merit consideration (1) that constraints imposed by the protein modulate hemin properties [1, 72-74) nd (2) that the protein participates intimately in the catalytic function(s) of the enzyme 17, 75). 

With these electron transport components, path can be created for the transfer of electrons from substrate to oxygen. Complexes I and IV obviously have enough energy change to support the phosphorylation of ADP to ATP, while complex III is marginal and complex II obviously does not have sufficient energy change. 

Table I. Effect of Deficiency on Electron Transport Components and Drug Enzymes in Guinea Pig Liver Microsomes...

Figure 5. Reversal of decreased electron transport components in vitamin C deficient guinea pigs with ascorbic acid (15).

All photosynthetic systems share common features. The conversion of light energy to a metabolically usable form is achieved by means of 1. lightabsorbing pigment-protein complexes, 2. electron transport components that produce vectorial electron transport within and around membrane boimd compartments, 3. membrane bound protein complexes, such as ATPases, that couple the relaxation of a transmembrane Ap to transport or synthesis, e.g. of ATP, and 4. reductases that reduce stable electron or hydrogen carriers that can be used to drive reductive... 

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