How many six-carbon compound are involved in Kreb's cycle?

Options

A. 3
B. 4
C. 2
D. 1

Answer

To determine how many six-carbon compounds are involved in 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 biochemical reactions used by all aerobic organisms to generate energy.

2. **Starting Compound**: The cycle begins with the combination of acetyl-CoA (a 2-carbon compound) and oxaloacetic acid (a 4-carbon compound). This reaction produces citrate, which is the first six-carbon compound in the cycle.

3. **Identifying Six-Carbon Compounds**:
- **Citrate**: The first six-carbon compound formed in the Krebs cycle.
- **Cis-Aconitic Acid**: An intermediate compound that is also a six-carbon compound formed from citrate.
- **Isocitrate**: Another stable six-carbon compound formed from cis-aconitic acid.

4. **Counting the Six-Carbon Compounds**:
- The three six-carbon compounds identified are:
- Citrate
- Cis-aconitic Acid
- Isocitrate
- Note that while citrate and isocitrate are stable compounds, cis-aconitic acid is an intermediate compound.

5. **Final Count**: Therefore, the total number of six-carbon compounds involved in the Krebs cycle is **3**.

### Conclusion:
The answer to the question is **3 six-carbon compounds** involved in the Krebs cycle.

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