What is true of urea biosynthesis

Options

A. Uric acid is starting point
B. Urea is synthesised in lysosomes
C. Urea cycle enzymes are located inside mitochondira
D. Urea is synthesised in kidney

Explanation

### Step-by-Step Solution

1. **Understanding Urea Biosynthesis**: Urea biosynthesis is a process that occurs in ureotelic organisms, which primarily excrete urea as their main nitrogenous waste.

2. **Location of Urea Cycle**: The urea cycle, which is responsible for the conversion of ammonia into urea, takes place in the mitochondria of liver cells.

3. **Enzymes Involved**: The enzymes that facilitate the urea cycle are located within the mitochondria. This is crucial for the synthesis of urea from ammonia.

4. **Source of Urea**: Urea is synthesized from ammonia, not uric acid. Uric acid is a different nitrogenous waste product and is not involved in the urea cycle.

5. **Excretion of Urea**: While urea is synthesized in the liver, it is then transported to the kidneys, where it is excreted from the body. Therefore, the synthesis occurs in the liver, not in the kidneys.

6. **Evaluating the Options**:
- **Option A**: "Uric acid is a starting point" - Incorrect, as ammonia is the starting point.
- **Option B**: "Urea is synthesized in lysosomes" - Incorrect, as urea is synthesized in mitochondria.
- **Option C**: "Urea cycle enzymes are located inside mitochondria" - Correct, as this is where the urea cycle occurs.
- **Option D**: "Urea is synthesized in kidney" - Incorrect, as it is synthesized in the liver.

7. **Conclusion**: The correct statement regarding urea biosynthesis is that "urea cycle enzymes are located inside mitochondria."