Which one is the last electron acceptor over ETC in oxidative phosphorylation

Options

A. `H_(2)`
B. Cyt`a_(3)`
C. Cyt b
D. `CO_(2)`.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the last electron acceptor in the electron transport chain (ETC) during oxidative phosphorylation.

2. **Identifying the Electron Transport Chain (ETC)**: The ETC is a series of protein complexes and other molecules that transfer electrons from electron donors like NADH and FADH2 to electron acceptors through redox reactions.

3. **Role of Complexes in ETC**: Electrons are transferred through various complexes in the ETC. The main complexes involved include:
- Complex I (NADH dehydrogenase)
- Complex II (Succinate dehydrogenase)
- Complex III (Cytochrome bc1 complex)
- Complex IV (Cytochrome c oxidase)

4. **Tracking Electron Flow**: The flow of electrons occurs as follows:
- Electrons from NADH and FADH2 are passed to Coenzyme Q (ubiquinone).
- From Coenzyme Q, electrons move to Complex III.
- After Complex III, electrons are transferred to cytochrome c.
- Finally, electrons are transferred to Complex IV.

5. **Identifying the Last Electron Acceptor**: The last step in the electron transport chain involves the transfer of electrons to oxygen. Specifically, electrons are accepted by cytochrome a3 (part of Complex IV) and ultimately transferred to molecular oxygen (O2), which is the final electron acceptor.

6. **Conclusion**: Therefore, the last electron acceptor in the electron transport chain during oxidative phosphorylation is **oxygen**, but in terms of the last protein complex involved, it is **cytochrome a3**.

**Final Answer**: The last electron acceptor in the electron transport chain during oxidative phosphorylation is **cytochrome a3**.

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