Compare the induced fit model and lock and key model for enzyme-substrate binding.

The lock and key model states that there is only one correctly sized substrate (key) for the activate site (lock) of each enzyme, therefore only one key can open each lock (react). The induced fit model however states that the enzyme active site is partially flexible and that substrate binding plays a role in determining the final shape of the active site. Furthermore, other molecules may not be the correct size and shape to induce the proper active site conformational change and therefore cannot react.