Oxygen is reduced to water in

Options

A. Fermentation
B. Calvin cycle
C. Electron transport
D. Krebs cycle

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks where oxygen is reduced to water. This is a key process in cellular respiration, specifically in the context of aerobic respiration.

2. **Identifying the Processes**: The options provided are fermentation, Calvin cycle, electron transport, and Krebs cycle. We need to analyze which of these processes involves the reduction of oxygen to water.

3. **Analyzing Each Option**:
- **Fermentation**: This process occurs in the absence of oxygen and does not involve the reduction of oxygen to water.
- **Calvin Cycle**: This is a part of photosynthesis and does not involve oxygen being reduced to water.
- **Krebs Cycle**: This cycle is part of aerobic respiration but does not directly involve the reduction of oxygen to water.
- **Electron Transport Chain (ETC)**: This is the final stage of aerobic respiration, where oxygen acts as the final electron acceptor.

4. **Focusing on the Electron Transport Chain**: In the ETC, electrons are transferred through a series of proteins, and at the end of this chain, oxygen accepts these electrons. When oxygen accepts electrons, it combines with protons (H⁺ ions) to form water (H₂O).

5. **Conclusion**: Since the electron transport chain is the process where oxygen is reduced to water, the correct answer is the electron transport chain.

6. **Final Answer**: Therefore, the answer to the question "Oxygen is reduced to water in" is **Electron Transport Chain** (Option C).

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