In ETS, the last electron acceptor is

Options

A. cytochrome - `alpha`
B. ATP
C. oxygen
D. water

Answer

To solve the question "In ETS, the last electron acceptor is," we need to understand the process of the Electron Transport Chain (ETS) and identify the final electron acceptor involved in this process.

### Step-by-Step Solution:

1. **Understanding Electron Transport Chain (ETS)**:
- The Electron Transport Chain is a series of protein complexes located in the inner mitochondrial membrane. It plays a crucial role in cellular respiration by transferring electrons from electron donors to electron acceptors.

**Hint**: Remember that ETS is a key part of the aerobic respiration process.

2. **Identifying Electron Donors**:
- In the ETS, the primary electron donors are NADH and FADH2. These molecules are generated during earlier stages of cellular respiration (like glycolysis and the Krebs cycle).

**Hint**: Think about where NADH and FADH2 come from in cellular respiration.

3. **Electron Transfer Process**:
- The electrons from NADH and FADH2 are passed through a series of complexes (Complex I, II, III, and IV) in the ETS. Each complex facilitates the transfer of electrons and helps pump protons across the mitochondrial membrane, creating a proton gradient.

**Hint**: Visualize the flow of electrons through the complexes.

4. **Final Electron Acceptor**:
- At the end of the electron transport chain, the electrons are ultimately transferred to molecular oxygen (O2), which acts as the final electron acceptor. This reaction leads to the formation of water (H2O) when oxygen combines with protons and electrons.

**Hint**: Recall that oxygen is essential for aerobic respiration and is often referred to as the final electron acceptor.

5. **Conclusion**:
- Therefore, the last electron acceptor in the Electron Transport Chain (ETS) is **Oxygen**.

### Final Answer:
The last electron acceptor in the Electron Transport Chain (ETS) is **Oxygen**.