Ubiquinone receives reducing equivalents from

Options

A. `NAD^(+)`
B. `FADH_(2)`
C. `NADH+H^(+)`
D. Both (2) & (3)

Answer

**Step-by-Step Solution:**

1. **Understanding Ubiquinone**: Ubiquinone, also known as coenzyme Q, is a crucial component of the electron transport chain located in the inner mitochondrial membrane. It plays a key role in transferring electrons from various donors to the final electron acceptor, which is oxygen.

2. **Sources of Reducing Equivalents**: Ubiquinone receives reducing equivalents primarily from two sources:
- **NADH**: This is produced during various metabolic processes, including the Krebs cycle. NADH donates electrons to the electron transport chain, which are transferred to ubiquinone.
- **FADH2**: This is another electron donor that comes from the Krebs cycle and other metabolic pathways. FADH2 also transfers electrons to ubiquinone.

3. **Electron Transfer Process**:
- When NADH is oxidized, it releases electrons and is converted back to NAD+. This process occurs with the help of dehydrogenase enzymes.
- Similarly, FADH2 is oxidized to FAD, releasing electrons that are also transferred to ubiquinone.

4. **Conclusion**: Therefore, ubiquinone receives reducing equivalents from both NADH and FADH2. The correct answer to the question is that ubiquinone receives reducing equivalents from both sources.

**Final Answer**: Ubiquinone receives reducing equivalents from both NADH and FADH2.

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