When two molecules of acetyl CoA enter the TCA cycle, net gain at the end of the cycle is

Options

A. `2NADH_(2) + 2FADH_(2) + 1GTP`
B. `3NADH_(2) + 2FADH_(2) + 2GTP`
C. `6NADH_(2) + 2FADH_(2) +2GTP`
D. `3NADH_(2) +1FADH_(2) + 4GTP`

Explanation

To solve the question regarding the net gain when two molecules of acetyl CoA enter the TCA cycle, we can break down the process step by step:

### Step-by-Step Solution:

1. **Understanding the TCA Cycle**: The TCA cycle, also known as the Krebs cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

2. **Entry of Acetyl CoA**: Each molecule of acetyl CoA that enters the TCA cycle will undergo a series of transformations. When two molecules of acetyl CoA enter the cycle, we need to account for the products generated from both.

3. **Products from One Molecule of Acetyl CoA**:
- From one acetyl CoA, the TCA cycle produces:
- 3 NADH
- 1 FADH2
- 1 GTP (which can be converted to ATP)

4. **Calculating for Two Molecules**: Since we have two molecules of acetyl CoA entering the cycle, we can multiply the products from one molecule by two:
- **NADH**: 3 NADH × 2 = 6 NADH
- **FADH2**: 1 FADH2 × 2 = 2 FADH2
- **GTP**: 1 GTP × 2 = 2 GTP

5. **Final Net Gain**: Therefore, the net gain at the end of the TCA cycle when two molecules of acetyl CoA enter is:
- 6 NADH
- 2 FADH2
- 2 GTP

6. **Conclusion**: The correct answer to the question is option C: 6 NADH + 2 FADH2 + 2 GTP.