The principal nitrogenous exretory compound in humans is syntheised

Options

A. in kidneys but eliminated mostly through liver
B. as well as elimated by kidneyys
C. in liver and also eliminated by rthe same through bile
D. in the liver, but eliminated mostly through kidneys.

Explanation

### Step-by-Step Solution:

1. **Identify the Principal Nitrogenous Excretory Compound**:
The principal nitrogenous excretory compound in humans is urea.

2. **Synthesis Location**:
Urea is synthesized primarily in the liver through a process known as the ornithine cycle (or urea cycle).

3. **Mechanism of Synthesis**:
- The synthesis begins with one molecule of carbon dioxide (CO2) reacting with two molecules of ammonia (NH3).
- This reaction is facilitated by the enzyme carbamoyl phosphate synthetase and involves the activation of CO2 by biotin, leading to the formation of carbamoyl phosphate.

4. **Formation of Citrulline**:
- The carbamoyl phosphate then reacts with ornithine, resulting in the formation of citrulline.

5. **Formation of Arginine**:
- Citrulline combines with another molecule of ammonia to form arginine.

6. **Breakdown of Arginine**:
- Arginine is then broken down into urea and ornithine.

7. **Excretion of Urea**:
- Urea, being the major nitrogenous excretory product, is primarily eliminated from the body through the kidneys.

8. **Conclusion**:
- Therefore, the correct statement is that urea is synthesized in the liver and eliminated mostly through the kidneys.