When one molecule of Glucose is completely oxidized in aerobic respiration, how many molecules of carbon dioxide are released in tricarboxylic acid cycle?

Options

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

Answer

To determine how many molecules of carbon dioxide are released in the tricarboxylic acid (TCA) cycle when one molecule of glucose is completely oxidized during aerobic respiration, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Glucose Oxidation**:
- One molecule of glucose (C6H12O6) undergoes glycolysis and is converted into two molecules of pyruvate (C3H4O3).

2. **Formation of Acetyl-CoA**:
- Each pyruvate is then converted into an acetyl-CoA (C2H3O-CoA) before entering the TCA cycle. During this conversion, one molecule of carbon dioxide (CO2) is released for each pyruvate. Since two pyruvate molecules are formed from one glucose molecule, this step releases a total of 2 CO2 molecules.

3. **Entering the TCA Cycle**:
- Each acetyl-CoA then enters the TCA cycle. Each acetyl-CoA contributes two carbon atoms to the cycle.

4. **Carbon Dioxide Production in the TCA Cycle**:
- In the TCA cycle, for each acetyl-CoA that enters, two molecules of carbon dioxide are released. Since there are two acetyl-CoA molecules from one glucose molecule, this results in an additional 4 CO2 molecules being released.

5. **Total Carbon Dioxide Released**:
- Adding the carbon dioxide released from the conversion of pyruvate to acetyl-CoA (2 CO2) and the carbon dioxide released during the TCA cycle (4 CO2), we get a total of 6 CO2 molecules released when one molecule of glucose is completely oxidized.

### Final Answer:
- Therefore, when one molecule of glucose is completely oxidized in aerobic respiration, a total of **6 molecules of carbon dioxide** are released in the tricarboxylic acid cycle.