BHU PMT BHU PMT (Screening) Solved Paper-2010

  • question_answer
    A competitive inhibitor of succinic dehydrogenase is

    A)  malonate                           

    B)  oxaloacetate

    C)   \[\text{ }\!\!\alpha\!\!\text{ -}\]ketoglutarate               

    D)  malate

    Correct Answer: B

    Solution :

                     Succinic dehydrogenase oxidised the succinate To fumarate. In eukaryotes, sucdnate dehydrogenase is tightly bound to the inner mitochondrial membrane, in prokaryotes to the plasma membrane. Electrons pass from succinate through FAD and iron-sulphur centres before entering the chain of electron carriers in the mitochondrial inner membrane. Malonate, an analogue of succinate is a strong competitive  inhibitor of succinate dehydrogenase and therefore, blocks the activity of citric acid cycle. In Krebs cycle, the reversible hydration of fumarate to malate is catalysed by rumarase enzyme. In the last reaction of Krebs cycle, NAD-linked L-malate dehydrogenase catalyses  the oxidation of L-malate to oxaloacetate. The isocitrate dehydrogenase in Krebs cycle catalyses oxidative decarboxylation of isocitrate to form a-ketoglutarate, which in next step through oxidative decarboxylation convened to succinyl Co-A.


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