One glucose on complete oxidation yields 36 ATP . During this oxidation of glucose , what is the contribution of the Krebs cycle via oxidative phosphorylation ?

Options

A. 11 ATP
B. 12 ATP
C. 22 ATP
D. 24 ATP

Answer

To determine the contribution of the Krebs cycle via oxidative phosphorylation in the complete oxidation of one glucose molecule, we can break down the process step by step:

### Step 1: Understand the Overall ATP Yield from Glucose Oxidation
One molecule of glucose, when completely oxidized, yields a total of 36 ATP. This total includes ATP produced from glycolysis, the transition phase, the Krebs cycle, and oxidative phosphorylation.

### Step 2: Analyze ATP Production in Glycolysis
In glycolysis, the following ATP is produced:
- **ATP directly produced**: 2 ATP
- **NADH produced**: 2 NADH, which can be converted to ATP via oxidative phosphorylation. Each NADH yields approximately 3 ATP.

Calculating the ATP from NADH:
- 2 NADH × 3 ATP/NADH = 6 ATP

Thus, the total ATP from glycolysis is:
- **Total from glycolysis** = 2 ATP + 6 ATP = **8 ATP**

### Step 3: Analyze ATP Production in the Transition Phase
During the transition phase (conversion of pyruvate to acetyl-CoA), the following occurs:
- **NADH produced**: 2 NADH, which also yields ATP via oxidative phosphorylation.

Calculating the ATP from NADH:
- 2 NADH × 3 ATP/NADH = 6 ATP

So, the total ATP from the transition phase is:
- **Total from transition phase** = 6 ATP

### Step 4: Analyze ATP Production in the Krebs Cycle
In the Krebs cycle, the following ATP is produced:
- **NADH produced**: 6 NADH
- **FADH2 produced**: 2 FADH2

Calculating the ATP from NADH and FADH2:
- 6 NADH × 3 ATP/NADH = 18 ATP
- 2 FADH2 × 2 ATP/FADH2 = 4 ATP

Thus, the total ATP from the Krebs cycle is:
- **Total from Krebs cycle** = 18 ATP + 4 ATP = **22 ATP**

### Step 5: Summarize Total ATP Yield
Now, we can summarize the total ATP yield from all phases:
- Glycolysis: 8 ATP
- Transition phase: 6 ATP
- Krebs cycle: 22 ATP

Adding these together gives:
- **Total ATP from all phases** = 8 ATP + 6 ATP + 22 ATP = 36 ATP

### Conclusion
The contribution of the Krebs cycle via oxidative phosphorylation is **22 ATP**.