Explain the lock and key mechanism in relation to enzymes.

The lock and key mechanism is a metaphor to explain the specificity of the enzymes active site and the substrate. In the same way only certain keys fit a lock, only certain substrates fit an enzyme's active site. The substrate is specific to a certain active site. When the correct substrate binds to the enzyme's active site, an Enzyme substrate complex is formed. The enzyme catalyses a reaction, an Enzyme product complex is formed and the product is released. The enzyme can then be reused again and again to catalyse more reactions.