Prostaglandin is

Options

A. Steroid
B. Carbohydrate
C. Amino acid
D. Fatty acid .

Answer

### Step-by-Step Solution:

1. **Understanding Prostaglandins**: Prostaglandins are a group of bioactive lipids that play a crucial role in various physiological processes. They are derived from fatty acids.

2. **Identifying the Precursor**: The primary precursor for the synthesis of prostaglandins is arachidonic acid, which is a polyunsaturated omega-6 fatty acid. Arachidonic acid is found in the phospholipids of cell membranes and is particularly abundant in the brain.

3. **Classification of Prostaglandins**: Prostaglandins are classified as lipid mediators. They are involved in autocrine and paracrine signaling, meaning they can act on the cells that produce them (autocrine) or on nearby cells (paracrine).

4. **Effects of Prostaglandins**: These lipid mediators have various effects on different tissues, including actions on platelets, endothelium (the inner lining of blood vessels), uterine tissues, and mast cells (involved in allergic responses).

5. **Examining the Options**:
- **Steroid**: Prostaglandins are not steroids; steroids are a different class of lipids (e.g., glucocorticoids, mineralocorticoids).
- **Carbohydrate**: Prostaglandins are not carbohydrates; carbohydrates are sugars.
- **Amino Acid**: Prostaglandins are not amino acids; amino acids are the building blocks of proteins.
- **Fatty Acid**: Prostaglandins are derived from fatty acids, specifically arachidonic acid.

6. **Conclusion**: Based on the above information, the correct classification for prostaglandins is that they are fatty acids.

### Final Answer:
**Prostaglandin is a fatty acid.**

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