Which of the following TCA cycle intermediates is also a metabolite in gluconeogenesis? O Pyruvate O Succinyl CoA O Oxaloacetate o Succinate Citrate
Ans). Option 3 oxaloacetate is the correct answer.
Explanation: Oxaloacetate which is an intermediate in the Citric Acid cycle is the precursor for gluconeogenesis.
In organisms where PEP carboxykinase is found only in mitochondria, oxaloacetate is converted to PEP (Phosphoenolpyruvate), which is then transported to the cytosol for gluconeogenesis. However, in organisms where oxaloacetate is converted into PEP in the cytosol, a problem arises.
Oxaloacetate cannot cross the mitochondrial membrane because the mitochondrial membrane has no transporter for oxaloacetate. So, oxaloacetate first reduces to malate by mitochondrial enzyme malate dehydrogenase, at the expense of NADH.
Malate then leaves the mitochondrion through a specific transporter in the inner mitochondrial membrane and in the cytosol is reoxidized to oxaloacetate, with the production of cytosolic NADH.
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