This is not a nitrogenous waste

Options

A. Creatinine
B. Citrulline
C. Purines
D. Allantoin

Answer

To determine which option is not a nitrogenous waste, we need to understand what nitrogenous wastes are and how they are formed. Here’s a step-by-step solution:

### Step 1: Understand Nitrogenous Wastes
Nitrogenous wastes are primarily the byproducts of protein metabolism. When proteins are broken down, they are converted into amino acids. The amino group from these amino acids is removed in a process called deamination, leading to the formation of various nitrogenous wastes.

**Hint:** Remember that nitrogenous wastes are mainly derived from the breakdown of proteins and amino acids.

### Step 2: Identify Common Nitrogenous Wastes
The major nitrogenous wastes include:
- Ammonia
- Urea
- Uric acid
- Creatinine
- Purines
- Allantoin

**Hint:** Focus on the common nitrogenous wastes produced during protein metabolism.

### Step 3: Analyze the Options
We need to look at the options provided and identify which one does not fit the category of nitrogenous waste. In this case, citrulline is mentioned as one of the options.

**Hint:** Compare each option against the definition of nitrogenous waste.

### Step 4: Determine the Nature of Citrulline
Citrulline is classified as a non-protein amino acid. It is involved in the urea cycle but is not a waste product itself; rather, it is an intermediate in the synthesis of urea from ammonia.

**Hint:** Recall that non-protein amino acids do not contribute to nitrogenous waste.

### Step 5: Conclusion
Since citrulline is a non-protein amino acid and not a breakdown product of proteins, it is not classified as a nitrogenous waste. Therefore, the correct answer to the question is that citrulline is not a nitrogenous waste.

**Hint:** Always check if the substance in question is a breakdown product or an intermediate in metabolic processes.

### Final Answer
Citrulline is not a nitrogenous waste.