Number of ATP molecules formed during aerobic respiration in break down of one glucose molecule via malate aspartate shuttle.

Options

A. 30
B. 38
C. 40
D. 24

Answer

To determine the number of ATP molecules formed during aerobic respiration from the breakdown of one glucose molecule via the malate-aspartate shuttle, we can follow these steps:

### Step 1: Glycolysis
- In glycolysis, one molecule of glucose is converted into two molecules of pyruvate. During this process, a net gain of 2 ATP and 2 NADH molecules is produced.

**ATP from Glycolysis: 2 ATP**

### Step 2: Pyruvate Decarboxylation
- Each pyruvate is converted into acetyl-CoA, releasing one molecule of CO2 and producing one NADH for each pyruvate. Since there are two pyruvate molecules, this results in 2 NADH.

**NADH from Pyruvate Decarboxylation: 2 NADH**

### Step 3: TCA Cycle (Krebs Cycle)
- Each acetyl-CoA enters the TCA cycle, which produces 3 NADH, 1 FADH2, and 1 ATP (or GTP) per acetyl-CoA. Since there are two acetyl-CoA molecules, the total yield from the TCA cycle is:
- 6 NADH (3 from each acetyl-CoA)
- 2 FADH2 (1 from each acetyl-CoA)
- 2 ATP (1 from each acetyl-CoA)

**ATP from TCA Cycle: 2 ATP**

### Step 4: Total NADH and FADH2 Calculation
- Total NADH produced:
- 2 NADH from glycolysis
- 2 NADH from pyruvate decarboxylation
- 6 NADH from TCA cycle
- **Total NADH = 10 NADH**

- Total FADH2 produced:
- 2 FADH2 from TCA cycle
- **Total FADH2 = 2 FADH2**

### Step 5: ATP Yield from NADH and FADH2
- Each NADH can produce approximately 2.5 ATP in the electron transport chain (ETC).
- Each FADH2 can produce approximately 1.5 ATP in the ETC.

Calculating the ATP yield:
- From 10 NADH:
- 10 NADH × 2.5 ATP/NADH = 25 ATP
- From 2 FADH2:
- 2 FADH2 × 1.5 ATP/FADH2 = 3 ATP

### Step 6: Total ATP Calculation
- Total ATP from glycolysis: 2 ATP
- Total ATP from TCA cycle: 2 ATP
- Total ATP from NADH: 25 ATP
- Total ATP from FADH2: 3 ATP

**Total ATP = 2 (glycolysis) + 2 (TCA) + 25 (NADH) + 3 (FADH2) = 32 ATP**

### Step 7: Accounting for the Malate-Aspartate Shuttle
- The malate-aspartate shuttle is more efficient than the glycerol-3-phosphate shuttle, allowing the 2 NADH from glycolysis to contribute to the production of 5 ATP (instead of 4 ATP with the glycerol-3-phosphate shuttle).

### Final Calculation
- Therefore, the total ATP yield from one glucose molecule via the malate-aspartate shuttle is:

**Total ATP = 32 ATP (from previous calculation) + 6 ATP (from 2 NADH via malate-aspartate shuttle) = 38 ATP**

### Conclusion
The number of ATP molecules formed during aerobic respiration in the breakdown of one glucose molecule via the malate-aspartate shuttle is **38 ATP**.

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