A ligand is a substance that interacts with a biomolecule to create a complex that is useful to living things. Binding is caused by intermolecular forces such as Van der Waals forces, hydrogen bonds, and ionic bonds. Biological processes can be either inhibited or activated by multivalent ligands. A typical endocytic method utilized by cells to internalize particles is the interaction of cell receptors with particle ligands, which causes the cell membrane to wrap the particle into a delivery vesicle. Strong inhibitory activity can be produced by multivalent ligand-receptor interactions with high functional affinities. Because they include several copies of a receptor-binding region, multivalent ligands can bind to receptors with great avidity and specificity, making them potent inhibitors.