CELL RESPIRATION
THE KREBS CYCLE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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I and II only
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I and III only
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II and III only
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I, II and III
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Detailed explanation-1: -Cyanide is a potent toxicant that produces a rapid onset, histotoxic anoxia by inhibiting mitochondrial oxidative phosphorylation (Way, 1984). Cyanide binds to the cytochrome c oxidase (CcOX) heme a3-CuB binuclear center to inhibit both cellular oxygen utilization and ATP production (Way, 1984).
Detailed explanation-2: -Cyanide has been long recognized as an inhibitor of mitochondrial electron transport due to its binding to the heme a3 prosthetic group in Complex IV (Cytochrome C oxidase [CCOx]). The shutdown of aerobic ATP generation is recognized as the primary mode of cyanide’s cytotoxic action in eukaryotes (1).
Detailed explanation-3: -Cyanide inhibits cytochrome oxidase by combining with Iron within the enzyme which results in the prevention of transport of electrons from cytochrome oxidase to oxygen.
Detailed explanation-4: -What effect would cyanide have on ATP synthesis? After cyanide poisoning, the electron transport chain can no longer pump electrons into the intermembrane space. The pH of the intermembrane space would increase, the pH gradient would decrease, and ATP synthesis would stop.