Question

The first stable compound of citric acid is
A.Citric acid
B.Pyruvic acid
C.Oxaloacetic acid
D.None of the above

Answer 1

Hint: Citric acid cycle is also known as the tricarboxylic acid cycle and is mainly known as the Krebs cycle.

Complete answer:
The aerobic respiration in plants has many steps, and one such step is the citric acid cycle which takes place after glycolysis and is responsible for providing energy to the cells.
In glycolysis, the glucose is oxidized to pyruvic acid through a series of reactions, then this pyruvic acid undergoes the link reaction where the pyruvic acid is converted to acetyl-CoA. After this acetyl-CoA enters the Krebs cycle.
The first step of the Krebs cycle is the reaction between Oxaloacetic acid with water and acetyl-CoA that leads to the formation of Citric acid that is the first stable product of the citric acid cycle.

Option A: Many reactions occur in the citric acid cycle but the first stable product that is formed in this citric acid cycle is citric acid obtained by reacting acetyl-CoA with Oxaloacetate and water. Therefore, this is the correct option.

All other options are irrelevant.

Hence, the correct answer is option (A)

Note: The Krebs cycle is a citric acid cycle That was discovered by scientist Hans Adolf Kreb in 1937, hence this cycle is also known as the Krebs cycle. The first stable product is citric acid undergoes isomerization to form isocitrate, after which many reactions occur that lead to the formation of alpha-ketoglutaric acid, then succinic acid, then malic acid, which again converts to oxaloacetate to restart the citric acid cycle.