Which of the following processes produce the maximum amount of ATP on the aerobic breakdown of one molecule of glucose ?

Options

A. Glycolysis
B. Kreb's
C. Electron transport system
D. Fermentation

Answer

To determine which process produces the maximum amount of ATP during the aerobic breakdown of one molecule of glucose, we can break down the entire process into its key stages: glycolysis, oxidative decarboxylation, the Krebs cycle, and the electron transport chain.

### Step-by-Step Solution:

1. **Glycolysis**:
- Glycolysis occurs in the cytoplasm and breaks down one molecule of glucose into two molecules of pyruvate.
- During glycolysis, **4 ATP** are produced directly (2 ATP are used, resulting in a net gain of **2 ATP**).
- Additionally, **2 NADH** molecules are produced.

2. **Oxidative Decarboxylation**:
- This process occurs in the mitochondria where pyruvate is converted into Acetyl-CoA.
- During oxidative decarboxylation, **0 ATP** are produced directly.
- However, **2 NADH** molecules are generated from the conversion of pyruvate to Acetyl-CoA.

3. **Krebs Cycle (Citric Acid Cycle)**:
- The Krebs cycle also occurs in the mitochondria and processes Acetyl-CoA.
- In one turn of the Krebs cycle, **2 ATP** are produced directly.
- Additionally, **6 NADH** and **2 FADH2** molecules are produced.

4. **Electron Transport Chain (ETC)**:
- The NADH and FADH2 produced in previous steps enter the ETC, which is located in the inner mitochondrial membrane.
- Each NADH can produce approximately **3 ATP**, and each FADH2 can produce approximately **2 ATP**.
- From glycolysis, we have **2 NADH** (yielding 6 ATP), from oxidative decarboxylation, we have **2 NADH** (yielding 6 ATP), and from the Krebs cycle, we have **6 NADH** (yielding 18 ATP) and **2 FADH2** (yielding 4 ATP).
- Therefore, the total ATP produced from the ETC is:
- From 10 NADH: \(10 \times 3 = 30 \, \text{ATP}\)
- From 2 FADH2: \(2 \times 2 = 4 \, \text{ATP}\)
- Total from ETC = **34 ATP**.

5. **Total ATP Calculation**:
- Now, we can sum up all ATP produced:
- Glycolysis: **2 ATP**
- Krebs Cycle: **2 ATP**
- Electron Transport Chain: **34 ATP**
- Total = \(2 + 2 + 34 = 38 \, \text{ATP}\).

### Conclusion:
The process that produces the maximum amount of ATP during the aerobic breakdown of one molecule of glucose is the **Electron Transport Chain**.