Question

In Kreb’s cycle ______.

• A. ADP is converted to ATP
• B. pyruvic acid is converted to CO₂ and H₂O
• C. glucose is converted in CO₂
• D. pyruvic acid is converted to ATP

Answer 1

The correct option is A

Explanation of the correct answer:

1. The Krebs cycle or TCA cycle (tricarboxylic acid cycle) or Citric acid cycle is a series of enzyme catalysed reactions occurring in the mitochondrial matrix, where acetyl-CoA (formed by the oxidative carboxylation of pyruvic acid) is oxidised to form carbon dioxide and water.

2. Krebs cycle or Citric acid cycle is the final pathway of oxidation of glucose, fats and amino acids.

3. Hence, in Kreb's cycle pyruvic acid is converted to $C{O}_2$ and $H_{2}O$ .

Explanation of the incorrect answers:

Option B:

1. The process of conversion of the ADP (adenosine diphosphate) into ATP (adenosine triphosphate) takes place at the mitochondrial membrane.
2. This occurs through the process of oxidative phosphorylation.

Option C:

1. The conversion of glucose into $C{O}_2$ is a two step process.
2. The first step is glycolysis in which glucose is converted into pyruvic acid.
3. The second step is Kreb's cycle in which the carboxylated product of pyruvic acid,i.e., acetyl-CoA is oxidised to form carbon dioxide and water.

Option D:

1. Again, pyruvic acid is not directly converted into ATP.

2. It involves Kreb's cycle and oxidative phosphorylation.

Final answer: In Kreb’s cycle pyruvic acid is converted to $C{O}_2$ and $H_{2}O$.