How much energy is conserved as ATP per mole of `O_2` reduced into `H_2O` ?

Options

A. 36
B. 38
C. 6
D. 36 in eukaryotes and 38 in prokaryotes.

Explanation

To determine how much energy is conserved as ATP per mole of O₂ reduced into H₂O, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Process**: When glucose (C₆H₁₂O₆) is metabolized in the presence of oxygen (aerobic respiration), it produces carbon dioxide (CO₂), water (H₂O), and energy in the form of ATP.

2. **ATP Production in Aerobic Respiration**: In the presence of oxygen, the complete oxidation of one mole of glucose yields approximately 38 ATP molecules.

3. **ATP Production in Anaerobic Conditions**: In the absence of oxygen (anaerobic respiration), the same amount of glucose yields only about 2 ATP molecules.

4. **Calculating the Contribution of Oxygen**: The difference in ATP production between aerobic and anaerobic respiration indicates the contribution of oxygen.
- Thus, the contribution of oxygen to ATP production is:
\[ 38 \, \text{ATP (aerobic)} - 2 \, \text{ATP (anaerobic)} = 36 \, \text{ATP} \]

5. **Relating Oxygen to ATP Production**: The complete oxidation of one mole of glucose involves the reduction of 6 moles of oxygen (O₂) to produce water (H₂O). Therefore, we can calculate the ATP produced per mole of oxygen:
- Since 36 ATP are produced from 6 moles of O₂:
\[ \text{ATP per mole of O₂} = \frac{36 \, \text{ATP}}{6 \, \text{O₂}} = 6 \, \text{ATP} \]

6. **Final Answer**: Thus, the amount of energy conserved as ATP per mole of O₂ reduced into H₂O is **6 ATP**.

### Summary:
The answer to the question is that 6 ATP are conserved for each mole of O₂ reduced into H₂O during aerobic respiration.