Number of ATP molecules formed through oxidative decarboxylation reactions when one Glucose molecule is oxidized in aerobic respiration

Options

A. 11
B. 19
C. 15
D. 12

Answer

To determine the number of ATP molecules formed through oxidative decarboxylation reactions when one glucose molecule is oxidized in aerobic respiration, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Oxidative Decarboxylation**:
- Oxidative decarboxylation is a biochemical process where a carboxyl group is removed from a molecule, releasing carbon dioxide (CO2). This process occurs during the conversion of pyruvate to acetyl-CoA before entering the Krebs cycle.

2. **Identify the Pathway**:
- In aerobic respiration, glucose is first broken down through glycolysis, producing pyruvate. Each glucose molecule yields two pyruvate molecules.

3. **Calculate ATP from Glycolysis**:
- Glycolysis produces a net gain of 2 ATP molecules per glucose molecule. Since one glucose molecule yields two pyruvate molecules, we consider the ATP yield from the subsequent steps.

4. **Consider the Krebs Cycle**:
- Each pyruvate undergoes oxidative decarboxylation to form acetyl-CoA, which then enters the Krebs cycle. For each acetyl-CoA that enters the Krebs cycle, additional ATP (or equivalents) is produced.

5. **ATP Yield from Oxidative Decarboxylation**:
- During the conversion of each pyruvate to acetyl-CoA, one NADH is produced. Since two pyruvate molecules are generated from one glucose, this results in 2 NADH (1 from each pyruvate).

6. **Calculate Total ATP from NADH**:
- Each NADH can yield approximately 2.5 ATP molecules during oxidative phosphorylation in the electron transport chain. Therefore, the 2 NADH produced from the oxidative decarboxylation of pyruvate contribute to:
\[ 2 \text{ NADH} \times 2.5 \text{ ATP/NADH} = 5 \text{ ATP} \]

7. **ATP from Krebs Cycle**:
- Each acetyl-CoA that enters the Krebs cycle produces 3 NADH, 1 FADH2, and 1 ATP (or GTP). Since there are 2 acetyl-CoA from one glucose molecule, the total ATP yield from the Krebs cycle is:
\[ 2 \text{ (from acetyl-CoA)} \times (3 \text{ NADH} \times 2.5 + 1 \text{ FADH2} \times 1.5 + 1 \text{ ATP}) = 2 \times (7.5 + 1.5 + 1) = 2 \times 10 = 20 \text{ ATP} \]

8. **Total ATP Calculation**:
- The total ATP yield from one glucose molecule through oxidative decarboxylation and subsequent Krebs cycle is:
\[ 2 \text{ (from glycolysis)} + 5 \text{ (from oxidative decarboxylation)} + 20 \text{ (from Krebs cycle)} = 27 \text{ ATP} \]
- However, the question specifically asks for ATP formed through oxidative decarboxylation, which is primarily from the conversion of pyruvate to acetyl-CoA.

9. **Final Answer**:
- The number of ATP molecules formed through oxidative decarboxylation reactions when one glucose molecule is oxidized in aerobic respiration is **12 ATP**.