Cadherins are

Options

A. Junctions of epithelial cells
B. Tumor suppressor genes
C. Cellular products that promote motility
D. Large glycoproteins of B-lymphocytes

Answer

**Step-by-Step Solution:**

1. **Understanding Cadherins**: Cadherins are a class of proteins that play a crucial role in cell adhesion. They are primarily involved in the binding of cells to each other, which is essential for the formation of tissues.

2. **Identifying the Type of Protein**: Cadherins are classified as type 1 transmembrane proteins. This means they span the cell membrane and have portions that extend into both the intracellular and extracellular environments.

3. **Function of Cadherins**: The main function of cadherins is to mediate cell-cell adhesion. This is particularly important in the context of epithelial tissues, where cells need to stick together to maintain the integrity of the tissue.

4. **Evaluating the Options**:
- **Option 1: Junctions of epithelial cells** - This is correct because cadherins are indeed involved in forming junctions between epithelial cells.
- **Option 2: Tumor suppressor genes** - This is incorrect. Tumor suppressor genes are involved in regulating cell growth and preventing cancer, but they are not cadherins.
- **Option 3: Cellular products that promote motility** - This is incorrect. Motility is generally associated with structures like cilia and flagella, not cadherins.
- **Option 4: Large glycoproteins of B lymphocytes** - This is also incorrect. While glycoproteins are present in B lymphocytes, they do not refer to cadherins.

5. **Conclusion**: Based on the evaluation of the options, the correct answer is that cadherins are **junctions of epithelial cells**.