The correct sequence in Krebs cycle is

Options

A. Oxaloacetic acid `to alpha`-ketoglutaric acid `to` Isocitric acid
B. Oxaloacetic acid `to` Isocitric acid `to alpha`-ketoglutaric acid
C. `alpha` ketoglutaric acid `to ` Isocitric acid `to` Oxaloacetic acid
D. Isocitric acid `to alpha` ketoglutaric acid `to` Oxaloacetic acid

Answer

To answer the question regarding the correct sequence in the Krebs cycle, we will outline the steps involved in the cycle and the order in which the compounds are formed.

### Step-by-Step Solution:

1. **Start with Oxaloacetate**: The Krebs cycle begins with oxaloacetate, which is a four-carbon compound.

2. **Formation of Citrate**: Oxaloacetate combines with acetyl-CoA (derived from pyruvate) to form citrate (also known as citric acid), a six-carbon compound.

3. **Conversion to Isocitrate**: Citrate is then converted into isocitrate through a rearrangement process.

4. **Formation of Alpha-Ketoglutarate**: Isocitrate is oxidized and decarboxylated to form alpha-ketoglutarate, a five-carbon compound.

5. **Formation of Succinyl-CoA**: Alpha-ketoglutarate undergoes another decarboxylation to form succinyl-CoA, a four-carbon compound.

6. **Conversion to Succinate**: Succinyl-CoA is then converted to succinate, releasing CoA and producing GTP (or ATP).

7. **Formation of Fumarate**: Succinate is oxidized to fumarate.

8. **Conversion to Malate**: Fumarate is hydrated to form malate.

9. **Regeneration of Oxaloacetate**: Finally, malate is oxidized to regenerate oxaloacetate, completing the cycle.

### Correct Sequence:
The correct sequence of compounds in the Krebs cycle is:
- Oxaloacetate → Citrate → Isocitrate → Alpha-Ketoglutarate → Succinyl-CoA → Succinate → Fumarate → Malate → Oxaloacetate