Select the correct sequence of formation of given intermediates of Krebs' cycle.

Options

A. Succinate `rarr` Malate `rarr` Fumarate`rarr` OAA
B. Fumarate `rarr` Succinate.`rarr` Malate`rarr` OAA
C. Succinate `rarr` Fumarate `rarr` Malate `rarr` OAA
D. Malate`rarr` Fumarate `rarr` Succinate `rarr` OAA

Answer

To solve the question regarding the correct sequence of formation of intermediates in the Krebs cycle, we will follow the steps of the cycle and identify the intermediates in the correct order.

### Step-by-Step Solution:

1. **Start with Acetyl CoA and Oxaloacetate**:
- The Krebs cycle begins when Acetyl CoA combines with Oxaloacetate to form Citrate (Citric Acid).
- **Hint**: Remember that Acetyl CoA is the starting point for the cycle.

2. **Formation of Citrate**:
- The first intermediate formed is Citrate (Citric Acid).
- **Hint**: Citrate is also known as citric acid and is the first product of the cycle.

3. **Conversion of Citrate to Isocitrate**:
- Citrate is then converted into Isocitrate through a rearrangement reaction.
- **Hint**: Isomerization occurs here.

4. **Formation of Alpha-Ketoglutarate**:
- Isocitrate is oxidized and decarboxylated to form Alpha-Ketoglutarate.
- **Hint**: This step involves the release of CO2.

5. **Formation of Succinyl CoA**:
- Alpha-Ketoglutarate is further processed to form Succinyl CoA.
- **Hint**: Another decarboxylation occurs here.

6. **Conversion of Succinyl CoA to Succinate**:
- Succinyl CoA is converted into Succinate, releasing CoA.
- **Hint**: This step generates GTP or ATP.

7. **Formation of Fumarate**:
- Succinate is then oxidized to form Fumarate.
- **Hint**: This step involves the enzyme succinate dehydrogenase.

8. **Conversion of Fumarate to Malate**:
- Fumarate is hydrated to form Malate.
- **Hint**: This is a simple addition of water.

9. **Formation of Oxaloacetate**:
- Finally, Malate is oxidized to regenerate Oxaloacetate.
- **Hint**: This completes the cycle and allows it to begin anew.

### Correct Sequence of Intermediates:
- The correct sequence of intermediates in the Krebs cycle is:
1. Succinate
2. Fumarate
3. Malate
4. Oxaloacetate

### Conclusion:
- Therefore, the correct option is the one that lists the intermediates in the order of Succinate → Fumarate → Malate → Oxaloacetate.