The isomerization of citrate to isocitrate: a) is the only unnecessary step of the citric acid cycleb) protects cells from the toxic effects of arsenite ionc) converts a tertiary alcohol, which cannot easily by oxidized, to a secondary alcohol that can be oxidizedd) is a major regulatory step for the citric acid cyclee) is an oxidation reaction

The correct answer is c converts a tertiary alcohol which cannot easily be oxidized to a secondary alcohol that can be oxidized.

Explanation:

Both citrate and isocitrate are isomers of each other and also very important metabolic intermediates of TCA cycle.

  Citrate is a tertiary alcohol that"s why it cannot be metabolized as it"s functional group is surrounded by many bulky groups.

 To overcome this problem citrate is converted to isocitrate which is a secondary alcohol that can easily be metabolized to generate alpha ketoglurate an important intermediate of TCA cycle.

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