In aerobic respiration, release of redox equivalents as H-atom for the first time in mitochondiral matrix is catalysed by

Options

A. PGAL dehydrogenase
B. Isocitrate dehydrogenase
C. Pyruvate dehydrogenase
D. `alpha-`KGA dehydrogenase

Answer

To solve the question regarding which enzyme catalyzes the release of redox equivalents as hydrogen atoms for the first time in the mitochondrial matrix during aerobic respiration, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Aerobic Respiration**:
- Aerobic respiration consists of several stages: glycolysis (occurs in the cytoplasm), the link reaction (occurs in the mitochondrial matrix), the Krebs cycle (also in the mitochondrial matrix), and the electron transport chain (in the inner mitochondrial membrane).

2. **Identifying the Link Reaction**:
- The link reaction connects glycolysis to the Krebs cycle. It involves the conversion of pyruvate (the end product of glycolysis) into acetyl-CoA, which enters the Krebs cycle.

3. **Enzymes Involved**:
- The question asks for the enzyme that catalyzes the release of redox equivalents as hydrogen atoms for the first time in the mitochondrial matrix.
- The relevant enzymes mentioned in the options are:
- a. PGAL dehydrogenase (in glycolysis)
- b. Isocitrate dehydrogenase (in Krebs cycle)
- c. Pyruvate dehydrogenase (in link reaction)
- d. Alpha-ketoglutarate dehydrogenase (in Krebs cycle)

4. **Analyzing Each Option**:
- **PGAL dehydrogenase**: This enzyme is involved in glycolysis, which occurs in the cytoplasm, not the mitochondrial matrix. Thus, it can be eliminated.
- **Isocitrate dehydrogenase**: This enzyme is part of the Krebs cycle but does not act in the mitochondrial matrix for the first time.
- **Pyruvate dehydrogenase**: This enzyme catalyzes the conversion of pyruvate to acetyl-CoA in the mitochondrial matrix and releases NADH + H+ (the redox equivalents).
- **Alpha-ketoglutarate dehydrogenase**: This enzyme is also part of the Krebs cycle and does not act first in the mitochondrial matrix.

5. **Conclusion**:
- The correct answer is **c. Pyruvate dehydrogenase**, as it is the enzyme that catalyzes the release of redox equivalents as hydrogen atoms for the first time in the mitochondrial matrix during aerobic respiration.