Homophoic interactions occur when an adhesion molecule on the surface of one cell binds to the same molecule on the surface of another cells. Thus, leading to selective adhesion between cells of the same type. Cadherins are also involved in selective adhesion between embryonic cells. Cadherins are also primarily responsible for the formation of stable junctions between cells in tissues. Tight junctions also separate apical from basolateral domains of the plasma membrane.
Tight junctions are the closest known contacts between adjacent cells.
Tight juctions appear to be formed by a network of protein strands that continues around the entire circumference of a cell. Each strand in this network seems to be composed of the transmembrane protein occludin . Gap junctions serve as direct connection between cytoplasm of adjacent cells. They provide open channels through plasma membranes, allowing ions and small molecules such as cAMP, to diffuse between neighboring cells. Thus Gap junctions couple metabolic activities and electric responses of cells they connect.