During the complete oxidation of glucose, the proportion of ATP formed by substrate-level phosphorylation is ....

Options

A. `100%`
B. `89.5%`
C. `10.5%`
D. `50%`

Answer

To solve the question regarding the proportion of ATP formed by substrate-level phosphorylation during the complete oxidation of glucose, we can follow these steps:

### Step 1: Understand the complete oxidation of glucose
The complete oxidation of glucose involves several metabolic pathways, primarily glycolysis, the Krebs cycle (also known as the citric acid cycle), and the electron transport chain (ETC).

### Step 2: Determine the total ATP produced
During the complete oxidation of one molecule of glucose, a total of 38 ATP molecules are produced. This includes ATP generated from both substrate-level phosphorylation and oxidative phosphorylation.

### Step 3: Identify ATP from substrate-level phosphorylation
Substrate-level phosphorylation occurs during glycolysis and the Krebs cycle. Specifically:
- Glycolysis produces 2 ATP through substrate-level phosphorylation.
- The Krebs cycle also produces 2 ATP through substrate-level phosphorylation.

### Step 4: Calculate total ATP from substrate-level phosphorylation
Adding the ATP produced from both glycolysis and the Krebs cycle gives:
\[ 2 \, (\text{from glycolysis}) + 2 \, (\text{from Krebs cycle}) = 4 \, \text{ATP} \]

### Step 5: Calculate the proportion of ATP from substrate-level phosphorylation
To find the proportion of ATP formed by substrate-level phosphorylation relative to the total ATP produced, we use the formula:
\[ \text{Proportion} = \left( \frac{\text{ATP from substrate-level phosphorylation}}{\text{Total ATP produced}} \right) \times 100 \]
Substituting the values:
\[ \text{Proportion} = \left( \frac{4}{38} \right) \times 100 \]

### Step 6: Perform the calculation
Calculating the above expression:
\[ \text{Proportion} = \left( \frac{4}{38} \right) \times 100 \approx 10.53\% \]

### Step 7: Conclusion
Thus, the proportion of ATP formed by substrate-level phosphorylation during the complete oxidation of glucose is approximately **10.5%**.

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