The text describes the first three reactions of a metabolic pathway. Complete the sentences. Not all the terms will be placed. In reaction 1 of the Krebs cycle, acetyl‑CoA formed in the pyruvate dehydrogenase reaction condenses with the four‑carbon compound to form with the elimination of coenzyme A. Since the product has three carboxyl groups, this pathway is referred to as the cycle. In reaction 2 of the Krebs cycle, this product then undergoes to form . The enzyme is called aconitase because the compound c i s ‑ aconitate cis‑aconitate is the of the reaction. Reaction 3 eliminates CO 2 CO2 to form the five‑carbon dicarboxylic acid . Oxidation also occurs, with electrons transferred from the substrate to . Consequently, this reaction is an oxidative decarboxylation.