For example, we have a variety of different types of proteins and enzymes found in a cell membrane that actually bind onto that cell membrane. And so these other sections of the enzyme can be responsible for actually adhering and binding onto the cell machinery. For example, the membrane of the cell. Now, property number five of enzymes and the active sides of enzymes is that active sites typically bind substrates reversibly via non covalent forces. So in property number one and two, we basically mentioned that inside the active side we have these special residues, the amino acids that contain the special side chain groups that are responsible for actually attaching and binding the substrate molecules. And the binding that takes place takes place via non covalent interactions such as hydrogen bonds, such as hydrophobic interactions and vandervals forces.