Question

Assertion: The first step in the TCA cycle is the condensation of Pyruvate with oxaloacetic acid and water.
Reason: This reaction is catalyzed by the enzyme pyruvate synthase.
(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.

Answer 1

Hint: The other name of the TCA cycle is the Krebs cycle is called the citric acid cycle. This cycle is used for the formation of energy by the process of aerobic respiration. In this process the oxidation of carbohydrates called acetyl, Co-A occurs.

Complete answer
The Krebs cycle takes place in the cell's mitochondria, helps to generate energy, and takes place immediately after glycolysis. The beginning of the cycle occurs when due to acetyl coenzyme A the pyruvic acid is formed, which then forms citric acid when combined along with oxalic acetic acid. During one cycle one ATP is produced and thus for 1 molecule of glucose 2 Krebs cycles are required. Therefore, 2 ATP molecules are produced.
The pyruvate produced in glycolysis is oxidized in the mitochondrial matrix to form Acetyl CoA, which then enters the second stage of cellular respiration, Kreb’s cycle. This is an aerobic process comprising 8 steps of chemical reactions which yield 2 molecules of ATP, 2 molecules of FADH2, 6 molecules of NADH, and 4 molecules of ${ CO }_{ 2 }$. ${ FADH }_{ 2 }$ is also an energy-carrying molecule that produces 1.5 ATP molecules through the ETC. The first actual step in the TCA cycle is the formation of citric acid and coA through condensation of the Acetyl CoA, Oxaloacetic acid, and water. The enzyme used here is the citrate synthetase.

${ Acetyl CoA }+{ OOA }+{ H }_{ 2 }O\xrightarrow { Sunlight\quad Energy } { Citrate }+{ CoA }$

There are 15 ATP molecules formed by one pyruvate molecule while 30 ATP molecules are formed by two pyruvate molecules. It is believed from the history that mitochondria were independently formed due to their energy-producing nature and thus the Krebs cycle occurs in the mitochondria and helps in the exchange of energy. In the case of prokaryotic cells, the TCA cycle occurs in the cytosol, unlike eukaryotic cells that occur in the inner mitochondrial membrane because in prokaryotic cells mitochondria remain absent.

So, the correct answer is ‘Both Assertion and Reason are incorrect’.

Note:
The citric acid cycle is also referred to as the tricarboxylic acid cycle (TCA cycle). This cycle consists of a series of reactions where the Acetyl coA is oxidized with the help of proteins, fats, and carbohydrates. This series of reactions take place in the aerobic organisms. This TCA cycle also helps in the production of various amino acids and NADH as a reducing agent.