Assertion: Krebs cycle is called tricarboxylic acid cycle.
Reason: The first product of krebs cycle is citric acid which is tricarboxylic in nature.
(a) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
(b) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
(c) Assertion is correct but Reason is incorrect
(d) Both Assertion and Reason are incorrect

Hint: The Krebs cycle occurs inside the mitochondrial matrix of the inner chamber. The citric acid is the first product formed in the Krebs cycle. There are 3-COOH groups present in the citric acid. The Krebs cycle is a part of cellular aerobic respiration.

Complete answer:
The Krebs cycle is also known as the citric acid cycle or TCA (tricarboxylic acid) cycle because the citric acid has 3- COOH groups and is the first product of the Krebs cycle. The Krebs cycle has 8 successive steps in its complete cycle.

- The significance of the Krebs cycle:
1. After the completion of the Krebs cycle, carbon compounds are formed which are necessary for the growth and maintenance of the cell. The formed products in the citric acid cycle are used in the synthesis of biomolecules like amino acids, nucleotides, chlorophyll, cytochromes, and fats, etc. Intermediates like succinyl- CoA take part in the formation of chlorophyll. Amino acids are formed from alpha- ketoglutaric acid, pyruvic acids, and oxaloacetic acid.
2. Krebs cycles release plenty of energy in the form of ATP (Adenosine triphosphate), required for various metabolic activities of the cell.
- The details of the Krebs cycle was given by sir Hans Krebs in pigeon muscles.
- The Krebs cycle occurs in most plants, animals, fungi, and many bacteria.
So, the correct answer is, ‘Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.’

Note: The Krebs cycle finishes the job of breaking the sugar molecule started in the glycolysis. Before the rather large molecules can enter the TCA cycle they are degraded into a two- carbon compound called acetyl coenzyme A (acetyl CoA). TCA- cycle is the second stage of cellular respiration, which is a three- stage process.