Answer:
1.Retenone is one of the inhibitors of NADH dehydrogenase in cells. NADH dehydrogenase is an enzyme that oxidizes co-factor NADH so that electrons flow;for Electron transport chain (ECT) set up at complex I could be available for the chemical potential energy generated set up for Proton Motive Force.(PMF) .
The PMF is needed for influx of protons for ATPs synthesis. <u>Therefore ingestion of rotenone hinders electron transfer sequence of the iron-sulfur centers in complex 1 to ubiquinone (co-enzyme Q) of membrane. Consequently, ECT will be reduced; PMF will not occur,with resultant reduction in ATP synthesis. This is an example of completive inhibititon, however if there is no available substrate to neutralize this effect from prolong exposure , the effects of toxicity can be high.</u>
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<u>2.</u> Antimycin, by stopping the oxidation of ubiquinone, prevents the ubiquinone -cycle of enzyme( NADH dehydrogenase) turn over.
Therefore Antimycin A acts as poison by blocking ATP synthesis in the mitochondria; which stops the electron transport chain sequence(ETC) though inhibition of election transfer from cytochrome b to cytochrome c1, with consequent buildup of QH2 concentrations in the cells.
3.<u> Antimycin is more toxic than Rotenone</u> ;because<u> it inhibits the activities of ubiqunone by preventing its oxidation to QH2; the final electron acceptor, in both complex I and II.</u> Thus in absence of electron acceptor in both complex I and II, both ATP synthesis and electron transport Chain are stopped.
<u>Rotenone, is less toxic because,</u> compare to Antimycin it only block availability of electrons for ECT sequence in complex I only,<u> but complex II electron flow is not affected by its inhibition.</u> Therefore the complex ii electron flow still ensures ECT progress ;although ATP synthesis may be slow.
Explanation: