Question

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????????‑aconitate is the of the reaction. Reaction 3 eliminates 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.

Answer 1

In reaction 1 of the Krebs cycle, acetyl‑CoA formed in the pyruvate dehydrogenase reaction condenses with the four‑carbon compound to form citrate 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 isocitrate. The enzyme is called aconitase because the compound cis‑aconitate is the intermediate product of the reaction. Reaction 3 eliminates CO2 to form the five‑carbon dicarboxylic acid α-cetoglutarate. Oxidation also occurs, with electrons transferred from the substrate to COO- . Consequently, this reaction is an oxidative decarboxylation.

In the image, you can see the reaction 2 in Krebs cycle is a two steps reaction with an intermediate cis-aconitase and a product called isocitrate.

Answer 2

Step-by-step explanation:

In the first step of Krebs cycle, pyruvate dehydrogenase condenses with oxalocyclate , a 4 carbon coumpound. It forms citrate with removal of CoA.. Citrate thus formed has 3 carboxylic acid group and hence this cycle is called TCA cycle or Tricarboxylic acid cycle

In reaction 2, This citrate thus formed undergoes isomerization to form isocitrate. The enzyme used here is called aconitase because this isomerization happens with cis-aconitate as the intermediate.

Further, in reaction 3, CO2 is eliminated to form \alpha -ketoglutarate which is a 5 carbon carboxylic acid. Here, oxidation occurs by electron transfer to NAD+which is converted to NADH

Final Answer:

First paragraph: Oxalocyclate, Citrate, Tricarboxylic acid

Second Paragraph: Isomerization, isocitrate, intermediate,

Third paragraph: \alpha-ketoglutarate, NAD+