The number of total ATP generated in TCA cycle per acetyl CoA molecule is

Options

A. 10
B. 12
C. 14
D. 24

Answer

To determine the total number of ATP generated in the TCA cycle (Krebs cycle) per acetyl CoA molecule, we can break down the process step by step.

### Step-by-Step Solution:

1. **Understanding Acetyl CoA Formation**:
- Acetyl CoA is formed from pyruvate, which is the end product of glycolysis. This conversion occurs before entering the TCA cycle.

2. **Entry into the TCA Cycle**:
- Acetyl CoA combines with oxaloacetic acid to form citrate, which is the first compound in the TCA cycle.

3. **Key Reactions in the TCA Cycle**:
- As the cycle progresses, several key reactions occur that produce electron carriers:
- **Isocitrate to Alpha-Ketoglutarate**: This conversion produces 1 NADH.
- **Alpha-Ketoglutarate to Succinyl CoA**: This conversion produces another NADH.
- **Succinyl CoA to Succinate**: This step directly produces 1 ATP (or GTP, which can be converted to ATP).
- **Succinate to Fumarate**: This conversion produces 1 FADH2.
- **Fumarate to Malate**: No ATP is produced here.
- **Malate to Oxaloacetate**: This conversion produces 1 NADH.

4. **Counting ATP from Electron Carriers**:
- Each NADH produced in the TCA cycle can generate approximately 3 ATP when it enters the electron transport chain.
- Each FADH2 produced can generate approximately 2 ATP.

5. **Total ATP Calculation**:
- From the TCA cycle per acetyl CoA:
- 3 NADH from isocitrate, alpha-ketoglutarate, and malate = 3 x 3 ATP = 9 ATP
- 1 FADH2 from succinate = 2 ATP
- 1 ATP directly from succinyl CoA conversion.
- Total = 9 ATP (from NADH) + 2 ATP (from FADH2) + 1 ATP = 12 ATP.

### Final Answer:
The total number of ATP generated in the TCA cycle per acetyl CoA molecule is **12 ATP**.