Question

The formation of Acetyl CoA from pyruvic acid involves

• A. reduction
• B. dehydration
• C. phosphorylation
• D. oxidative decarboxylation

Answer 1

The correct option is D oxidative decarboxylation

Pyruvate, which is the product of glycolysis cannot participate directly in Krebs' cycle. It has to enter mitochondria through a specific transport protein pyruvate translocase. It undergoes oxidative decarboxylation i.e the removal of the carboxyl group to produce ${\mathrm{CO}}_2$ and NADH (reduced nicotinamide adenine dinucleotide).

The product combines with sulphur containing coenzyme A to form acetyl CoA or activated acetate. The reaction occurs in the presence of an enzyme complex pyruvate dehydrogenase (made up of a decarboxylase, lipoic acid, TPP, transacetylase and ${\mathrm{Mg}}^{2+}$).

Reduction reaction refers to the addition or gain of electrons. Dehydration refers to the removal of $H_{2}O$. Phosphorylation refers to the addition of ${{\mathrm{PO}}_4}^{3-}$