What are the models for enzyme action and how to remember the differences?

The two models to explain the actions of enzymes with substrates are the Lock and Key model & Induced fit model. In lock and key the enzyme is the lock and the substrate is the key. As with a lock and the key that opens it the shapes must be complementary and this shape can not change. Induced fit looks at the active site of enzymes as being slightly more flexible and initially uncomplementary. It suggests that it is the binding of the substrate to enzyme that causes the active site to change into a complementary shape and allow the enzyme-substrate complex to form.