The urea is formed from an amino acid

Options

A. lysine
B. cysteine
C. arginine
D. methionine

Answer

**Step-by-Step Solution:**

1. **Understanding Urea Formation**: Urea is a waste product formed in the liver as a result of protein metabolism. It is produced from the breakdown of amino acids and ammonia.

2. **Identifying the Role of Amino Acids**: Among the various amino acids, some play a direct role in the urea cycle, which is the process that converts ammonia, a toxic byproduct of amino acid breakdown, into urea for excretion.

3. **Analyzing the Options**: We have four amino acids to consider: Lysine, Cysteine, Arginine, and Methionine. We need to determine which of these is directly involved in the formation of urea.

4. **Evaluating Each Option**:
- **Lysine**: This amino acid does not have a direct role in the urea cycle.
- **Cysteine**: Similar to lysine, cysteine does not directly contribute to urea formation.
- **Arginine**: This amino acid is directly involved in the urea cycle. It is converted into urea through a series of enzymatic reactions.
- **Methionine**: Like lysine and cysteine, methionine does not directly participate in urea production.

5. **Conclusion**: Based on the evaluation, arginine is the amino acid that is directly involved in the formation of urea. Therefore, the correct answer is **Arginine**.

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