Sequence of organic acids in Krebs cycle is

Options

A. `"Citric acid" rarr "oxalosuccinic acid" rarr "isocitric acid"`
B. `"Citric acid" rarr "isocitric acid" rarr "oxalosuccinic acid"`
C. `"Isocitric acid" rarr "oxalosuccinic acid" rarr "citric acid"`
D. `"Oxalosuccinic acd" rarr "isocitric acId" rarr "citric acid."`

Answer

To answer the question regarding the sequence of organic acids in the Krebs cycle, we need to understand the key components and steps involved in this metabolic pathway. The Krebs cycle, also known as the citric acid cycle or TCA cycle, involves a series of chemical reactions used by all aerobic organisms to generate energy.

### Step-by-Step Solution:

1. **Identify the Starting Compound**:
- The Krebs cycle begins with Acetyl-CoA, which is derived from carbohydrates, fats, and proteins. Acetyl-CoA combines with oxaloacetate to form citric acid (citrate).

2. **Formation of Citric Acid**:
- Acetyl-CoA (2 carbon) combines with oxaloacetate (4 carbon) to form citric acid (6 carbon). This is the first step of the Krebs cycle.

3. **Conversion of Citric Acid to Isocitrate**:
- Citric acid is then converted into isocitrate through a rearrangement reaction.

4. **Oxidative Decarboxylation of Isocitrate**:
- Isocitrate is oxidized and decarboxylated to form α-ketoglutarate (5 carbon), releasing CO2 and reducing NAD+ to NADH.

5. **Formation of Succinyl-CoA**:
- α-Ketoglutarate undergoes another oxidative decarboxylation to form succinyl-CoA (4 carbon), producing another molecule of CO2 and reducing another NAD+ to NADH.

6. **Conversion of Succinyl-CoA to Succinate**:
- Succinyl-CoA is converted to succinate, and during this process, GTP (or ATP) is produced.

7. **Oxidation of Succinate to Fumarate**:
- Succinate is oxidized to fumarate, reducing FAD to FADH2 in the process.

8. **Hydration of Fumarate to Malate**:
- Fumarate is hydrated to form malate.

9. **Oxidation of Malate to Oxaloacetate**:
- Finally, malate is oxidized back to oxaloacetate, reducing NAD+ to NADH.

10. **Cycle Completion**:
- The oxaloacetate produced can then combine with another Acetyl-CoA to continue the cycle.

### Sequence of Organic Acids in the Krebs Cycle:
1. **Citrate (Citric Acid)**
2. **Isocitrate**
3. **α-Ketoglutarate**
4. **Succinyl-CoA**
5. **Succinate**
6. **Fumarate**
7. **Malate**
8. **Oxaloacetate**

### Final Answer:
The correct sequence of organic acids in the Krebs cycle is:
**Citrate → Isocitrate → α-Ketoglutarate → Succinyl-CoA → Succinate → Fumarate → Malate → Oxaloacetate**