What's the significance of lock and key model?

The lock and key model explains how a single substrate binds to the active site of the enzyme. According to this model, one specific substrate binds to one specific enzyme in a similar manner in which only one specific key can fit into and open a specific lock. In the lock and key model, the substrate is considered to be the key and the enzyme is the lock. Only a substrate with a shape and size that precisely complements the shape and size of the active site of the enzyme can bind tightly to that enzyme. If the shape and size of the substrate does not precisely complement the shape and size of the active site of an enzyme, it cannot bind to that enzyme. According to the lock and key model, the enzyme is a rigid structure. The shape of the active site does not undergo any changes or modifications during the binding process.