Reduction is the term used when conversion of ……… takes place

Options

A. (a) nitrate to nitrite
B. (b) nitrite to nitrate
C. (c) ammonia to nitrogen
D. (d) All of the above

Answer

**Step-by-Step Solution:**

1. **Understanding Reduction**: Reduction is a chemical process where a substance gains electrons or hydrogen, or loses oxygen. In biological terms, it often refers to the conversion of compounds in a way that decreases their oxidation state.

2. **Identifying the Context**: In the context of nitrogen metabolism, reduction is particularly relevant in the nitrogen cycle, where nitrogen undergoes various transformations.

3. **Nitrogen Cycle Overview**: The nitrogen cycle involves several key processes: nitrogen fixation, nitrification, and denitrification. During these processes, nitrogen is converted from one form to another, including from inorganic to organic forms and vice versa.

4. **Focusing on Reduction**: In the nitrogen cycle, reduction reactions typically occur when nitrate (NO3-) is converted to nitrite (NO2-) or further down to nitrogen gas (N2). This is a reduction process because the nitrogen is being reduced in its oxidation state.

5. **Identifying the Correct Conversion**: Among the options provided:
- A) Nitrate to nitrite is a reduction reaction.
- B) Nitrite to nitrate is an oxidation reaction.
- C) Ammonia to nitrogen is an oxidation reaction (via anammox).
- D) All of the above is incorrect since not all options represent reduction.

6. **Conclusion**: The correct answer to the question is that reduction is the term used when the conversion of nitrate to nitrite takes place.

**Final Answer**: Reduction is the term used when conversion of nitrate to nitrite takes place.

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