Which one does not match with regard to biological activity ?

Options

A. Creatinine
B. Renin
C. Gastrin
D. Oxytocin.

Answer

To solve the question "Which one does not match with regard to biological activity?", we will analyze each option provided in the context of their biological roles.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are creatinine, renin, gastrin, and oxytocin.

2. **Analyze Creatinine**:
- Creatinine is a metabolic waste product produced from the metabolism of creatine, which is primarily found in muscle tissue. It is excreted from the body through urine and does not have any biological activity related to hormonal or enzymatic functions.

3. **Analyze Renin**:
- Renin is a protease enzyme secreted by the kidneys. It plays a crucial role in the renin-angiotensin-aldosterone system (RAAS), which regulates blood pressure and fluid balance. Therefore, renin is biologically active and functions as an enzyme.

4. **Analyze Gastrin**:
- Gastrin is a peptide hormone that stimulates the secretion of gastric acid in the stomach. It is involved in the digestive process, indicating that it has significant biological activity as a hormone.

5. **Analyze Oxytocin**:
- Oxytocin is a hormone produced by the posterior pituitary gland. It is involved in various physiological functions, including uterine contractions during childbirth and the release of milk during lactation. Thus, oxytocin is also biologically active.

6. **Compare the Biological Activities**:
- Renin, gastrin, and oxytocin are all enzymes or hormones that play active roles in physiological processes. In contrast, creatinine is merely a waste product and does not participate in any biological activity related to enzyme or hormone functions.

7. **Conclusion**:
- Based on the analysis, the option that does not match with regard to biological activity is **creatinine**.

### Final Answer:
- The one that does not match with regard to biological activity is **creatinine**.