Question

Krebs cycle starts with the formation of six carbon compound by reaction between

• A. Malic acid and acetyl CoA
• B. Succinic acid and pyruvic acid
• C. Fumaric acid and pyruvic acid
• D. Acetyl CoA and oxaloacetic acid

Answer 1

Answer: (D)

Acetyl CoA and oxaloacetic acid

Krebs cycle starts with condensation of acetyl-CoA with oxaloacetate (OAA, 4C) to form citrate (6C) and is catalyzed by enzyme citrate synthase. Link reaction of aerobic respiration decarboxylates pyruvic acid into acetyl CoA which in turn enters Krebs's cycle. Malate is dehydrogenated in 8${}^{th}$ step of the cycle to continue the supply of OAA which in turn then reacts with acetyl-CoA. The correct answer is D.