Answer:
<u>Tight junctions </u>
Explanation:
Many cells in the tissues are connected to each other and also to the extracellular matrix at some specialized points of contact called as the cell junction. They can be classified into the following types-
1. Tight Junctions
2. Communicating Junctions
3. Anchoring Junctions
1. Tight Junction: They are also named as zonula occludens and are mediated by two trans membrane proteins namely claudins and occludins. Claudins and occludins interact with each other in such a way that they make the closest contact between the adjacent cells and likewise prevent the passage of any molecules and or ions across the epithelial layer in the spaces present between the cells.
2. Gap Junction: Gap junctions are a type of the communicating junctions which serves as direct connections between the cytoplasm of the different cells. They also act as a channel which allows the inorganic ions, signal molecules, water soluble molecules and many other molecules thus coupling the cells both electrically and metabolically.
3. Desmosomes: Desmosomes are a type of anchoring junctions which are button like points of intercellular contact which helps in bonding the neighboring cells together. They bear a dense cytoplasmic plaque which is responsible for the connection of the cytoskeleton to the transmembrane linker proteins thus responsible for the connection of cell-cell.
Since tight junctions do not permit the movement of any molecules from one side of the membrane to the other side, voltage and ligand gated channels would not be required in these junctions.
