The last step in the TCA cycle is the oxidation of malate. This reaction is esse

Question

The last step in the TCA cycle is the oxidation of malate. This reaction is essential in order to regenerate oxaloacetate for subsequent oxidation of acetylCoA to produce NADH. However, the G of this reaction is + 7.1 kcal/mol making it unfavorable. This reaction proceeds when the energy state of the cell is low because

a) the TCA cycle does not follow normal rules of thermodynamics.

b) oxaloacetate can be bypassed to allow acetylCoA to enter the TCA cycle.

c) ATP can be used for energy in this reaction to overcome the unfavorable G.

d) the mitochondrial concentration of oxaloacetate remains very low.

e) the TCA cycle can be reversed to use malate to restore oxaloacetate.

Explanation / Answer

C) ATP can be used for energy in this reaction to overcome the unfavourable G.

Reason: This reaction is catalysed by malate dehydrogenase yields 6ATP molecules which helps to overcome the unfavourable G.

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