How many ATP molecules are formed from three molecules of acetyl CoA in Krebs cycle excluding electron transport chain ?

Options

A. 5
B. 3
C. 6
D. 33

Answer

To determine how many ATP molecules are formed from three molecules of acetyl CoA in the Krebs cycle (excluding the electron transport chain), 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 occurs in the mitochondria and processes acetyl CoA derived from carbohydrates, fats, and proteins.

2. **Acetyl CoA Input**: Each molecule of acetyl CoA enters the Krebs cycle and undergoes a series of reactions. The question specifies that we are considering three molecules of acetyl CoA.

3. **ATP Production in the Krebs Cycle**: During the Krebs cycle, each turn of the cycle produces one molecule of GTP (which is equivalent to ATP). This occurs when succinyl CoA is converted to succinate. Therefore, for each molecule of acetyl CoA that enters the cycle, one GTP (or ATP) is produced.

4. **Calculating Total ATP from Three Acetyl CoA**: Since each acetyl CoA produces one ATP (or GTP), for three molecules of acetyl CoA, the total ATP produced would be:
\[ \text{Total ATP} = 3 \text{ (from 3 acetyl CoA)} \]

5. **Conclusion**: Therefore, the total number of ATP molecules formed from three molecules of acetyl CoA in the Krebs cycle, excluding the electron transport chain, is **3 ATP molecules**.