Gastrin is

Options

A. Hormone
B. A Enzyme
C. A Nutrient
D. Digestive secretion.

Answer

**Step-by-Step Solution:**

1. **Understanding Gastrin**: The question asks about gastrin and its classification. It is important to identify what gastrin is in the context of biological functions.

2. **Identifying the Options**: The options provided are hormone, enzyme, and nutrient digestive secretion. We need to analyze each option to determine which one accurately describes gastrin.

3. **Definition of Hormone**: A hormone is a chemical messenger produced by glands in the body that travels through the bloodstream to target organs or tissues to regulate physiological processes.

4. **Production of Gastrin**: Gastrin is produced by G-cells, which are located in the lining of the stomach and the upper part of the small intestine. This is a crucial point as it indicates where gastrin is synthesized.

5. **Function of Gastrin**: Gastrin plays a significant role during meals. It stimulates the stomach to release gastric acid, which is essential for the digestion of food. This function aligns with the definition of a hormone as it regulates a specific physiological process.

6. **Eliminating Other Options**:
- **Enzyme**: Enzymes are biological catalysts that speed up chemical reactions. Gastrin does not catalyze any reactions; therefore, it is not an enzyme.
- **Nutrient Digestive Secretion**: Nutrients are substances that provide nourishment. Gastrin does not provide nourishment directly; rather, it facilitates digestion by stimulating gastric acid secretion. Hence, it is not classified as a nutrient or digestive secretion.

7. **Conclusion**: Based on the analysis, gastrin is correctly classified as a hormone. Therefore, the correct answer to the question is "hormone."

**Final Answer**: Gastrin is a hormone.

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