Which of the following metabolities enter the TCA cycle during glucose oxidation ?

Options

A. Oxaloacetic acid
B. Pyruvic acid
C. Acetyl CoA
D. Malic acid

Answer

To determine which metabolites enter the TCA cycle during glucose oxidation, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Glycolysis**:
- Glucose is first broken down into two molecules of pyruvic acid through a series of reactions known as glycolysis. This process occurs in the cytoplasm of the cell.

2. **Conversion of Pyruvic Acid**:
- Each molecule of pyruvic acid is then converted into acetyl-CoA through a process called oxidative decarboxylation. This reaction also releases carbon dioxide (CO2) and produces NADH.

3. **Entry into the TCA Cycle**:
- The acetyl-CoA produced from pyruvic acid is the primary metabolite that enters the TCA cycle (also known as the Krebs cycle or citric acid cycle). Each molecule of glucose produces two molecules of acetyl-CoA, which then enter the TCA cycle.

4. **Formation of Citric Acid**:
- Once inside the TCA cycle, acetyl-CoA combines with oxaloacetic acid to form citric acid, which is the first stable compound in the cycle.

5. **Summary of Key Metabolites**:
- The main metabolites that enter the TCA cycle during glucose oxidation are:
- **Acetyl-CoA** (from pyruvic acid)
- **Oxaloacetic acid** (which combines with acetyl-CoA to initiate the cycle)

### Conclusion:
The correct answer to the question is **acetyl-CoA** (Option 3), as it is the metabolite that directly enters the TCA cycle during glucose oxidation.