In Krebs cycle

Options

A. Acetyl coenzyme A undergoes 4 oxidations and 2 decarboxylations
B. Pyruvic acid undergoes 4 oxidations and 2 decarboxylations
C. TCA undergoes 4 oxidations and 4 de-carboxylations
D. OAA undergoes 4 oxidations and two decarboxylations

Answer

**Step-by-Step Solution:**

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the tricarboxylic acid (TCA) cycle, is a crucial metabolic pathway that takes place in the mitochondria of cells. It is responsible for the oxidation of acetyl-CoA to produce energy.

2. **Components Involved**: The primary substrate for the Krebs cycle is acetyl-CoA, which is derived from carbohydrates, fats, and proteins. The cycle involves various intermediates, including citrate, isocitrate, alpha-ketoglutarate, succinyl-CoA, succinate, fumarate, malate, and oxaloacetate (OAA).

3. **Oxidation and Decarboxylation**: In the Krebs cycle, acetyl-CoA undergoes a series of reactions that include oxidation and decarboxylation.
- **Oxidation** refers to the loss of electrons, while **decarboxylation** refers to the removal of carbon dioxide (CO2).

4. **Identifying Oxidation Steps**:
- The first oxidation occurs when isocitrate is converted to alpha-ketoglutarate.
- The second oxidation occurs when alpha-ketoglutarate is converted to succinyl-CoA.
- The third oxidation occurs when succinate is converted to fumarate.
- The fourth oxidation occurs when malate is converted to oxaloacetate (OAA).

5. **Identifying Decarboxylation Steps**:
- The first decarboxylation occurs simultaneously with the first oxidation (isocitrate to alpha-ketoglutarate).
- The second decarboxylation occurs when alpha-ketoglutarate is converted to succinyl-CoA.

6. **Summary of Reactions**: In total, when acetyl-CoA enters the Krebs cycle:
- There are **4 oxidation reactions**.
- There are **2 decarboxylation reactions**.

7. **Conclusion**: Based on the analysis, the correct statement about the Krebs cycle is that acetyl-CoA undergoes 4 oxidations and 2 decarboxylations.

**Final Answer**: Acetyl-CoA undergoes 4 oxidations and 2 decarboxylations in the Krebs cycle.

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