Net gain of ATP molecules of each molecule of glucose in fermentation is

Options

A. 8
B. 10
C. 4
D. 2

Answer

To determine the net gain of ATP molecules from each molecule of glucose during fermentation, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Glucose Breakdown**:
- Glucose, a 6-carbon molecule, undergoes glycolysis, which is the first step in both aerobic and anaerobic respiration.

2. **Glycolysis Process**:
- During glycolysis, one molecule of glucose is converted into two molecules of pyruvic acid. This process occurs in the cytoplasm and does not require oxygen.

3. **ATP Production in Glycolysis**:
- In glycolysis, a net gain of 2 ATP molecules is produced per molecule of glucose. Additionally, 2 NADH molecules are generated.

4. **Fermentation Pathways**:
- In the absence of oxygen, pyruvic acid can undergo fermentation. There are two types of fermentation:
- Lactic acid fermentation
- Alcoholic fermentation

5. **NADH Utilization**:
- During fermentation, the NADH produced in glycolysis is used to convert pyruvic acid into either lactic acid or ethanol. This conversion regenerates NAD+, which is necessary for glycolysis to continue.

6. **ATP Yield from Fermentation**:
- Importantly, fermentation itself does not produce additional ATP beyond what was generated during glycolysis. Therefore, the total ATP yield from one molecule of glucose during fermentation remains at 2 ATP.

7. **Conclusion**:
- Thus, the net gain of ATP molecules from each molecule of glucose in fermentation is **2 ATP molecules**.

### Final Answer:
The net gain of ATP molecules from each molecule of glucose in fermentation is **2 ATP molecules**.

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