Terminal oxidation in ETC is

Options

A. (a) stoppage of oxidation
B. (b) final release of protons
C. (c) only step where actual oxidation using `O_2` occurs
D. (d) ETS initiation

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Electron Transport Chain (ETC):**
- The Electron Transport Chain (ETC) is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions. This process is crucial for cellular respiration.

2. **Role of Reduced Coenzymes:**
- The ETC primarily utilizes reduced coenzymes, namely NADH and FADH2, which are generated during earlier stages of cellular respiration (like glycolysis and the Krebs cycle). These coenzymes donate electrons to the chain.

3. **Process of Electron Transfer:**
- As electrons move through the ETC, they pass through various protein complexes located in the inner mitochondrial membrane. This movement of electrons is coupled with the pumping of protons (H+) from the mitochondrial matrix into the intermembrane space, creating a proton gradient.

4. **Terminal Oxidation:**
- The terminal oxidation refers to the final step of the ETC, where molecular oxygen acts as the final electron acceptor. This step is crucial because it allows the entire chain to continue functioning by preventing a backlog of electrons.

5. **Oxidative Phosphorylation:**
- The process of using oxygen to facilitate the conversion of ADP to ATP is known as oxidative phosphorylation. This is where the energy from the electrons is used to synthesize ATP, the energy currency of the cell.

6. **Evaluating the Options:**
- Option A: "Stoppage of oxidation" - This is incorrect because oxidation occurs at this step.
- Option B: "Final release of protons" - This is also incorrect; while protons are involved, the focus is on ATP synthesis.
- Option C: "Only step where actual oxidation using oxygen occurs" - This is the correct answer, as this step involves the actual oxidation process with oxygen.
- Option D: "ETS initiation" - This is incorrect because terminal oxidation is the last step, not the initiation.

7. **Conclusion:**
- The correct answer to the question "Terminal oxidation in ETC is" is Option C: "Only step where actual oxidation using oxygen occurs."

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