During ETS oxygen is present at the end of respiratory chain as terminal acceptor of electron. It accepts electron from :-

Options

A. A mobile electron carrier
B. Two different electron carriers simultaneously
C. An iron and copper containing electron carrier
D. A mobile H-carrier

Answer

**Step-by-Step Solution:**

1. **Understanding the Electron Transport Chain (ETC):** The ETC is the final stage of cellular respiration, specifically aerobic respiration. It occurs in the inner mitochondrial membrane and involves a series of molecules that transfer electrons.

2. **Role of Oxygen:** Oxygen acts as the terminal electron acceptor in the ETC. This means that at the end of the electron transport chain, oxygen receives the electrons that have been passed along the chain.

3. **Source of Electrons:** The electrons that enter the ETC come from the Krebs cycle (also known as the citric acid cycle). In this cycle, glucose is broken down, and electrons are released as part of the metabolic process.

4. **Electron Transfer:** The electrons are transferred from one molecule to another within the ETC. These molecules include various electron carriers, primarily cytochromes, which are proteins that contain heme groups.

5. **Final Reaction:** At the end of the electron transport chain, the electrons are ultimately transferred to oxygen. This reaction also involves protons (H+ ions) to form water (H2O). Without oxygen, the entire process of the ETC would halt, and ATP production would cease.

6. **Specific Electron Carrier:** The specific electron carrier that transfers electrons to oxygen is cytochrome a3. This molecule contains iron and copper and plays a crucial role in the final step of the electron transport chain.

**Final Answer:** Oxygen accepts electrons from cytochrome a3, which is an iron and copper-containing electron carrier.

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