During Krebs cycle various 6C, 5C, 4C intermediates are formed and converted to other compounds. The correct sequence of these intermediates, is :-

Options

A. Isocitrate, oxalosuccinate, oxaloacetate, succinyl CoA
B. `alpha` -ketoglutarate, succinyl CoA, oxaloacetate, Malate
C. Cis aconitic acid, -ketoglutarate, succinate, fumaric acid
D. Cis aconitic acid, fumarate, -ketoglutarate, succinyl CoA

Answer

To solve the question regarding the correct sequence of 6C, 5C, and 4C intermediates formed during the Krebs cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the citric acid cycle or TCA cycle, is a series of chemical reactions used by all aerobic organisms to generate energy. It involves the conversion of acetyl-CoA into carbon dioxide and energy-carrying molecules.

2. **Identifying Key Intermediates**:
- The cycle starts with **acetyl-CoA** (2C) combining with **oxaloacetate** (4C) to form **citrate** (6C).
- Citrate (6C) is then converted into **isocitrate** (6C).
- Isocitrate (6C) is oxidized to form **alpha-ketoglutarate** (5C).
- Alpha-ketoglutarate (5C) is further oxidized to form **succinyl-CoA** (4C).
- Succinyl-CoA (4C) is converted into **succinate** (4C).
- Succinate (4C) is then oxidized to form **fumarate** (4C).
- Fumarate (4C) is hydrated to form **malate** (4C).
- Finally, malate (4C) is oxidized to regenerate **oxaloacetate** (4C), completing the cycle.

3. **Correct Sequence of Intermediates**:
- The sequence of intermediates formed during the Krebs cycle can be summarized as follows:
- **Citrate (6C) → Isocitrate (6C) → Alpha-ketoglutarate (5C) → Succinyl-CoA (4C) → Succinate (4C) → Fumarate (4C) → Malate (4C) → Oxaloacetate (4C)**

### Final Sequence:
- The correct sequence of intermediates in the Krebs cycle is:
- **Citrate (6C) → Isocitrate (6C) → Alpha-ketoglutarate (5C) → Succinyl-CoA (4C) → Succinate (4C) → Fumarate (4C) → Malate (4C) → Oxaloacetate (4C)**