Ubiquianone carries electrons from

Options

A. Complex III to complex IV
B. Complex I to complex II
C. Complex II to complex III only
D. Complex I or II to complex III

Answer

**Step-by-Step Solution:**

1. **Understanding Ubiquinone**: Ubiquinone, also known as coenzyme Q, is a lipid-soluble molecule that plays a crucial role in the electron transport chain (ETC) within cellular respiration.

2. **Role in Electron Transport Chain**: Ubiquinone functions as an electron carrier. It is involved in transferring electrons from two key complexes in the electron transport chain: Complex I (NADH dehydrogenase) and Complex II (succinate dehydrogenase).

3. **Electron Sources**:
- Complex I receives electrons from NADH (produced during glycolysis and the Krebs cycle).
- Complex II receives electrons from FADH2 (produced during the Krebs cycle).

4. **Pathway of Electrons**: After accepting electrons from Complex I and Complex II, ubiquinone transports these electrons to Complex III (cytochrome bc1 complex) in the electron transport chain.

5. **Final Connection**: Ubiquinone connects Complex III to Complex IV (cytochrome c oxidase) via cytochrome c, facilitating the transfer of electrons and contributing to the proton gradient used for ATP synthesis.

6. **Conclusion**: Therefore, ubiquinone carries electrons from Complex I and Complex II to Complex III in the electron transport chain.

**Final Answer**: Ubiquinone carries electrons from Complex I and Complex II to Complex III.

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