two of the steps in the oxidative decarboxylation of pyruvate (steps 4 and 5 in the figure) do not involve any of the three carbons of pyruvate, yet are essential to the operation of the pyruvate dehydrogenase (pdh) complex. Why are steps 4 and 5 essential to the operation of the PDH complex?• They transfer a thiol group from coenzyme A to acetyl lipoyllysine.• They reduce the disulfide bond in oxidized lipoyllysine.• They reoxidize the reduced lipoamide cofactor.• They catalyze the synthesis of hydroxyethyl thiamine pyrophosphate (TPP).

The two steps catalyzed by dihydrolipoyl dehydrogenase (E3) are required to regenerate the oxidized form of lipoate, bound to dihydrolipoyl transacetylase, from the dihydrolipoyl (reduced) form produced in the oxidation of pyruvate. First, FAD is reduced to FADH2 to reoxidize the dihydrolipoate, then NAD+ is reduced to NADH to reoxidize the FADH2 to complete the reaction.

What three steps are included in the breakdown of pyruvate ?

Pyruvate, which is created during glycolysis, enters the mitochondria to start aerobic respiration. Pyruvate is converted to acetyl CoA to start aerobic respiration. Decarboxylation, NAD+ reduction, and coenzyme A attachment are the three steps that make up this conversion.

To create acetyl CoA, pyruvate is subjected to oxidative decarboxylation. A byproduct of glycolysis is pyruvic acid. In the presence of the pyruvate dehydrogenase complex, pyruvate is oxidized.

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