How many ATP molecules are formed by oxidative phosphorylation from NADH produced during single Krebs cycle ?

Options

A. 6
B. 18
C. 30
D. 9

Answer

To determine how many ATP molecules are formed by oxidative phosphorylation from NADH produced during a single Krebs cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the citric acid cycle, involves a series of chemical reactions used by all aerobic organisms to generate energy. During this cycle, NAD+ is reduced to NADH at several key steps.

2. **Identifying NADH Production**: In one complete turn of the Krebs cycle, three molecules of NADH are produced. These steps include:
- The conversion of isocitrate to alpha-ketoglutarate.
- The conversion of alpha-ketoglutarate to succinyl-CoA.
- The conversion of malate to oxaloacetate.

3. **ATP Yield from NADH**: Each NADH molecule that enters the electron transport chain can generate approximately 2.5 to 3 ATP molecules through oxidative phosphorylation. For simplicity, we will use the common estimate of 3 ATP per NADH.

4. **Calculating Total ATP from NADH**: Since there are three NADH produced in one Krebs cycle:
- Total ATP = Number of NADH × ATP per NADH
- Total ATP = 3 NADH × 3 ATP/NADH = 9 ATP

5. **Final Answer**: Therefore, from the NADH produced during a single Krebs cycle, a total of 9 ATP molecules are formed through oxidative phosphorylation.

### Conclusion:
The answer to the question is that 9 ATP molecules are formed by oxidative phosphorylation from NADH produced during a single Krebs cycle.

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