In aerobic respiration, there is complete oxidation of pyruvate by the stepwise removal of all the hydrogen atoms, releasing ______________ molecules of `CO_(2)`

Options

A. Two
B. Three
C. Four
D. Six

Answer

To solve the question regarding the number of carbon dioxide molecules released during the complete oxidation of pyruvate in aerobic respiration, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Pyruvate Formation**:
- Pyruvate is produced from glucose during glycolysis. This process occurs in the cytoplasm and results in two molecules of pyruvate for each molecule of glucose.

2. **Entry into Mitochondria**:
- After glycolysis, pyruvate enters the mitochondria where it undergoes further processing for aerobic respiration.

3. **Conversion to Acetyl-CoA**:
- In the mitochondria, each pyruvate molecule is converted into acetyl-CoA. During this conversion, one molecule of carbon dioxide (CO₂) is released for each pyruvate. Since one glucose molecule produces two pyruvate molecules, this step releases a total of 1 CO₂ per pyruvate x 2 pyruvate = 2 CO₂.

4. **Krebs Cycle (TCA Cycle)**:
- The acetyl-CoA then enters the Krebs cycle (also known as the TCA cycle). For each acetyl-CoA that enters the cycle, two additional molecules of CO₂ are released. Since one glucose molecule produces two acetyl-CoA, this step releases a total of 2 CO₂ per acetyl-CoA x 2 acetyl-CoA = 4 CO₂.

5. **Total CO₂ Released**:
- Adding the CO₂ released from both stages:
- From the conversion of pyruvate to acetyl-CoA: 2 CO₂
- From the Krebs cycle: 4 CO₂
- Therefore, the total CO₂ released from the complete oxidation of one glucose molecule (which yields two pyruvate) is 1 (from pyruvate to acetyl-CoA) + 2 (from each acetyl-CoA in Krebs cycle) = 3 CO₂.

6. **Final Answer**:
- Thus, the complete oxidation of pyruvate in aerobic respiration releases **3 molecules of CO₂**.

### Final Answer:
The answer is **3** molecules of CO₂.