The net gain of ATP molecules in glycolysis during aerobic respiration is

Options

A. 0
B. 2
C. 4
D. 8

Answer

To determine the net gain of ATP molecules in glycolysis during aerobic respiration, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Glycolysis**:
- Glycolysis is the first step in aerobic respiration that occurs in the cytoplasm of the cell. It breaks down one molecule of glucose (a 6-carbon sugar) into two molecules of pyruvate (a 3-carbon compound).

2. **ATP Production in Glycolysis**:
- During glycolysis, a total of 4 ATP molecules are produced through substrate-level phosphorylation.

3. **ATP Utilization in Glycolysis**:
- However, 2 ATP molecules are consumed in the initial steps of glycolysis to convert glucose into glucose-6-phosphate and fructose-1,6-bisphosphate.

4. **Calculating Net Gain of ATP**:
- To find the net gain of ATP, we subtract the ATP used from the ATP produced:
- ATP produced: 4
- ATP used: 2
- Net gain = 4 ATP (produced) - 2 ATP (used) = 2 ATP

5. **Considering NADH Production**:
- Additionally, glycolysis produces 2 NADH molecules. Each NADH can be converted to ATP in the electron transport chain, yielding approximately 3 ATP per NADH under aerobic conditions.
- Therefore, 2 NADH x 3 ATP/NADH = 6 ATP.

6. **Total ATP Calculation**:
- Adding the ATP from NADH to the net gain from glycolysis:
- Net gain from glycolysis: 2 ATP
- ATP from NADH: 6 ATP
- Total ATP = 2 + 6 = 8 ATP

7. **Conclusion**:
- The net gain of ATP molecules in glycolysis during aerobic respiration is 8 ATP.

### Final Answer:
The net gain of ATP molecules in glycolysis during aerobic respiration is **8 ATP**.

---