How many `FADH_(2)` molecule are formed during Krebs cycle?

Answer

To determine how many FADH2 molecules are formed during the Krebs cycle (also known as the citric acid cycle or TCA cycle), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Krebs Cycle**: The Krebs cycle occurs in the mitochondrial matrix and is a crucial part of cellular respiration. It processes acetyl-CoA, which is derived from glucose after glycolysis.

2. **Know the Inputs**: Each glucose molecule, after glycolysis, is converted into two molecules of pyruvate. Each pyruvate is then converted into acetyl-CoA, which enters the Krebs cycle.

3. **Identify the Products**: During one turn of the Krebs cycle, several products are generated, including NADH, ATP (or GTP), and FADH2.

4. **Focus on FADH2 Production**: FADH2 is produced specifically during the conversion of succinic acid to fumaric acid. This reaction is catalyzed by the enzyme succinate dehydrogenase.

5. **Count the FADH2 Molecules**: For each turn of the Krebs cycle, one FADH2 molecule is produced. Since one glucose molecule leads to two acetyl-CoA molecules entering the Krebs cycle, the cycle turns twice for each glucose molecule.

6. **Final Calculation**: Therefore, for one glucose molecule, the total FADH2 produced is:
- 1 FADH2 per cycle × 2 cycles = 2 FADH2 molecules.

### Conclusion:
Thus, the total number of FADH2 molecules formed during the Krebs cycle from one glucose molecule is **2 FADH2 molecules**.

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