Multiple choice Krebs cycle starts with the formation of a 6 carbon atom by chemical reaction between malic acid and acetyl coenzyme A oxaloacetic acid and acetyl coenzyme A fumaric acid and pyruvic acid succinic acid and acetyl coenzyme A succinic acid and fumaric acid Reveal answer Fill a bubble to check yourself B Correct answer Explanation Oxaloacetic acid and acetyl coenzyme A forms 6 C citrate molecule.