Characteristic smell of urine is due to

Options

A. Urea
B. Uric acid
C. Urinod substance
D. Pus

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the characteristic smell of urine and which substance is responsible for it.

2. **Analyzing the Options**: The options given are:
- Urea
- Uric acid
- Urinode substance
- Pus

3. **Describing Normal Urine**: Normal urine is typically clear, pale yellow, and does not have a strong smell. The odor can be associated with certain chemical compounds.

4. **Identifying the Odor Components**: The characteristic smell of urine is often loosely associated with ammonia and several volatile acids. Fresh urine has a mild odor, while fermented urine has a stronger, more offensive odor primarily due to ammonia.

5. **Examining Urea and Uric Acid**: Urea and uric acid are byproducts of protein metabolism. When they break down, they can produce ammonia, but they are not the primary substances responsible for the characteristic smell.

6. **Identifying the Correct Substance**: Recent research has identified a specific substance known as "urinode" (C6H8O8) as the main contributor to the characteristic smell of urine. This substance was discovered by researchers Dane and Hartman.

7. **Eliminating Incorrect Options**:
- **Pus**: This is a thick fluid produced in infected tissues and is not related to the smell of urine.
- **Urea and Uric Acid**: While they contribute to ammonia production, they do not directly impart the characteristic smell.

8. **Conclusion**: The correct answer to the question is the "urinode substance," which is responsible for the characteristic smell of urine.

### Final Answer:
The characteristic smell of urine is due to the **urinode substance**.

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