Question

In Krebs cycle, OAA accept acetyl CoA to form
a. Citric acid
b. Oxalosuccinate
c. Fumarate
d. Succinyl CoA

Answer 1

Krebs cycle is a series of chemical reactions performed by all the organisms that utilise the process of aerobic respiration to release the energy that is stored by the oxidation of acetyl-CoA obtained from carbohydrate, fat, and protein.

Complete step-by-step answer:
Let’s discuss the above options and find the correct answer:
- Citric acid: Krebs cycle is also known as the citric acid cycle or tricarboxylic acid cycle. The cycle starts with the participation of the acetyl group with oxaloacetic acid and water to produce citric acid. The reaction is catalyzed by the enzymes citrate synthase and one molecule of CoA is released.
- Oxalosuccinate: The substrate of the citric acid cycle is oxalosuccinic acid which is acted upon by the enzymes isocitrate dehydrogenase. The salts and esters of the oxalosuccinic acid are known as oxalosuccinate. Oxalosuccinate is the unstable 6- carbon compound in the citric acid cycle.
- Fumarate: The reversible hydration of fumarate is catalyzed by the enzyme fumarase. It is present in the Krebs cycle which functions in the metabolism of amino acids.
- Succinyl CoA: Succinyl CoA is oxidized to oxaloacetic acid to continue the Krebs cycle. During the conversion of succinyl-CoA into succinic acid, a molecule of GTP is synthesized and this is the substrate-level phosphorylation.
Hence, the correct option is A.

Note: The continued oxidation of acetyl-CoA is required by the cycle. Oxaloacetic acid is the first member of the citric acid cycle and it is required for the continuous process of the cycle.