The binding site has a 3-dimensional shape to fit the chemical it interacts with. This shape is very important to how it works. The body produces substances which match binding sites and interact with them. The interaction sets off changes. For example it might cause a muscle cell to contract or a nerve impulse to move along a nerve.
Scientists study diseases to find out how they are caused.
Often the problem occurs at a particular binding site. The active compound of a medicine is made to match that particular binding site. Imagine a binding site that releases an electrical nerve impulse . These compounds have the same binding shape as the body's chemical. Therefore they interact at the binding site in the same way as the body's chemical.