Number of oxygen atoms required for complete oxidation of pyruvic acid is

Options

A. 6
B. 12
C. 3
D. 0

Answer

To determine the number of oxygen atoms required for the complete oxidation of pyruvic acid, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Pyruvic Acid**:
- Pyruvic acid is a 3-carbon compound produced during glycolysis, which is the breakdown of glucose (a 6-carbon compound).

2. **Conversion to Acetyl-CoA**:
- In aerobic respiration, pyruvic acid is converted into acetyl-CoA, a 2-carbon compound, releasing one molecule of carbon dioxide (CO2) in the process. This means that from one molecule of pyruvic acid, we are left with 2 carbons.

3. **TCA Cycle (Krebs Cycle)**:
- Acetyl-CoA enters the TCA cycle (Krebs cycle), where it undergoes a series of reactions. In this cycle, each acetyl-CoA results in the production of additional carbon dioxide and reducing agents (NADH and FADH2).

4. **Total Reducing Agents Produced**:
- From one molecule of pyruvic acid, we can derive 4 NADH and 1 FADH2 through the complete oxidation process (including the TCA cycle).

5. **Electron Transport Chain (ETC)**:
- The reducing agents (NADH and FADH2) donate electrons to the electron transport chain (ETC). For every pair of electrons transferred, one oxygen atom is required to form water (H2O).

6. **Calculating Oxygen Atoms**:
- Each NADH and FADH2 will ultimately require oxygen atoms for complete oxidation.
- Since 4 NADH and 1 FADH2 are produced, we need to account for the total number of electrons:
- 4 NADH = 8 electrons
- 1 FADH2 = 2 electrons
- Total = 10 electrons

7. **Oxygen Requirement**:
- Since each oxygen atom can accept 2 electrons, the total number of oxygen atoms required is:
- Total electrons (10) ÷ 2 = 5 oxygen atoms.

8. **Final Calculation**:
- However, we also need to account for the oxygen atoms that were released as carbon dioxide during the conversion of pyruvic acid to acetyl-CoA. This adds an additional 1 oxygen atom.
- Therefore, the total number of oxygen atoms required for the complete oxidation of one molecule of pyruvic acid is:
- 5 (from NADH and FADH2) + 1 (from CO2) = 6 oxygen atoms.

### Conclusion:
The number of oxygen atoms required for the complete oxidation of pyruvic acid is **6 oxygen atoms**.

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