What is the total gain of energy during anaerobic respiration

Options

A. Two ATP
B. One ATP
C. Four ATP
D. Three ATP

Answer

### Step-by-Step Solution:

1. **Understanding Anaerobic Respiration**:
- Anaerobic respiration occurs in the absence of oxygen and primarily involves glycolysis.

2. **Glycolysis Overview**:
- Glycolysis is the first step in both aerobic and anaerobic respiration. It converts glucose into pyruvate and occurs in the cytoplasm of the cell.

3. **ATP Consumption in Glycolysis**:
- During glycolysis, 2 ATP molecules are consumed in the initial steps:
- One ATP is used to convert glucose to glucose-6-phosphate.
- Another ATP is used to convert fructose-6-phosphate to fructose-1,6-bisphosphate.
- Therefore, a total of 2 ATP are lost in these steps.

4. **ATP Production in Glycolysis**:
- Glycolysis produces a total of 4 ATP molecules through substrate-level phosphorylation:
- Two ATP molecules are produced when converting glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate.
- Two ATP molecules are produced when converting phosphoenolpyruvate (PEP) to pyruvate.

5. **Net ATP Gain Calculation**:
- To find the net gain of ATP during anaerobic respiration, we subtract the ATP consumed from the ATP produced:
- Total ATP produced = 4 ATP
- Total ATP consumed = 2 ATP
- Net gain = 4 ATP (produced) - 2 ATP (consumed) = 2 ATP

6. **Conclusion**:
- The total gain of energy (in terms of ATP) during anaerobic respiration is **2 ATP**.