What is the definition of self-destructive behaviors?

patterns of behaviors that involve self-inflicted harm or abuse
a common personality disorder characterized by long-lasting, rigid pattern of thought and behavior
a mental disorder characterized by episodes of mood swings between depression and mania
a medical condition characterized by persistent, excessive worry

Cell adhesions are transmembrane proteins that connect two cell membranes together.

Explanation:

A transmembrane protein is an integral type of membrane protein that can penetrate in between bilayers of cellular membranes. They are the pathways that facilitate ionic and molecular transport in between cells.  

Cell adhesion molecules found scattered over the cell surface bind or stick to adjacent cells by interacting with specific molecules through the process of cell adhesion. These molecules are glycoproteins that act as transmembrane proteins and mediates both cell-to-cell and cell-to-extracellular matrix transportation of materials.

These adhesions take place through triggering of intracellular responses and signaling, gene expression, and cytoskeletal organization. Integrin, cadherins, and IgCAMs are major classes of cell adhesion molecules.