Which of the following process makes direct use of oxygen ?

Options

A. (a) Glycolysis
B. (b) Fermentation
C. (c) Electron transport chain
D. (d) Krebs cycle

Answer

To determine which process makes direct use of oxygen, let's analyze each option step by step:

### Step-by-Step Solution:

1. **Glycolysis**:
- Glycolysis is the process where glucose is converted into pyruvate, resulting in the production of ATP.
- This process occurs in the cytoplasm and does not require oxygen, making it anaerobic.
- **Conclusion**: Glycolysis does not directly use oxygen. (Incorrect option)

2. **Fermentation**:
- Fermentation is a metabolic process that converts glucose into pyruvate and then into either ethanol or lactic acid, depending on the type of fermentation.
- This process also occurs in the absence of oxygen (anaerobic).
- **Conclusion**: Fermentation does not directly use oxygen. (Incorrect option)

3. **Electron Transport Chain (ETC)**:
- The Electron Transport Chain is a series of protein complexes located in the inner mitochondrial membrane.
- It generates ATP through the transfer of electrons and protons, with molecular oxygen acting as the final electron acceptor.
- **Conclusion**: The ETC directly uses oxygen to produce ATP. (Correct option)

4. **Krebs Cycle**:
- The Krebs cycle (also known as the citric acid cycle) involves the conversion of pyruvate into acetyl-CoA and further reactions that produce NADH and FADH2.
- While the Krebs cycle itself does not use oxygen directly, it relies on the products generated by the ETC, which requires oxygen.
- **Conclusion**: The Krebs cycle is indirectly dependent on oxygen but does not directly use it. (Incorrect option)

### Final Answer:
The process that makes direct use of oxygen is **C. Electron Transport Chain**.

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