Ornithine cycle is related to

Options

A. Respiration
B. Excretion
C. Digestion
D. Nutrition

Answer

**Step-by-Step Solution:**

1. **Understanding the Ornithine Cycle**: The ornithine cycle, also known as the urea cycle, is a series of chemical reactions that occur in the liver. It is responsible for converting ammonia, which is toxic, into urea, which can be safely excreted from the body.

2. **Location of the Cycle**: The ornithine cycle takes place in both the mitochondria and the cytoplasm of liver cells. This dual location is important for the different stages of the cycle.

3. **Key Reactions in the Cycle**:
- In the mitochondria, ornithine is converted into citrulline.
- In the cytoplasm, citrulline is converted into argininosuccinic acid, which then releases fumaric acid and produces arginine.
- Finally, arginine is converted back into ornithine, and during this process, urea is released.

4. **Significance of Urea**: Urea is a major excretory product in ureotelic animals (animals that excrete nitrogen in the form of urea), including humans. This indicates that the cycle is crucial for the elimination of nitrogen waste from the body.

5. **Conclusion**: Since the primary function of the ornithine cycle is to convert ammonia into urea for excretion, it is directly related to the process of excretion.

**Final Answer**: The ornithine cycle is related to **Excretion** (Option 2).

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