Most receptors are proteins that traverse the cell membrane with a binding site on the extracellular region. The binding process is also identical, involving the same kind of intermolecular binding forces and induced fit. The heart has more β– than α– adrenergic receptors. This means that drugs that are selective for β-adrenergic receptors will act on the heart rather than on tissues which are rich in α-adrenergic receptors. Since the receptor is an integral part of the ion channel, the effects of a receptor binding to its messenger are felt almost immediately by the cell as ions flow through the channel. The receptor can bind another G protein and so the process repeats itself for as long as the chemical messenger is bound to the receptor. The design of compounds that switch off the tyrosine kinase activity of such receptors may be of interest in fighting cancer.