Explain the lock and key enzyme hypothesis

Enzymes are specific: meaning that an enzyme's active site is complementary to a particular substrate. In the lock and key hypothesis, a substrate that is complementary to the enzyme binds to the enzyme's active site. This forms and enzyme-substrate complex (ESC). This destabilises bonds in the substrate and causes it to catabolise to form the product. Hence an enzyme product complex is formed. The products are then released by the enzyme.