What is an enzyme and how does it work?

An enzyme is a biological catalyst (something that speeds up a chemical reaction), which is a protein, a chain made of many amino acid molecules. An enzyme has its own unique three-dimensional structure, which allows it to bind to one specific kind of substrate (substance) only.How it works:The lock and key model can be used to explain this. Just imagine a key that fits into a specific lock and opens the door, the opening of the door can be imagined as the chemical reaction, the lock as the active site of the enzyme and the key as the substrate.There is a site on the enzyme that is complementary in shape to that of its substrate, this is called the active site. The substrate binds to the active site of the enzyme under suitable conditions which leads to the formation of an enzyme-substrate complex. The chemical reaction occurs and at the end the product is released from the active site and the enzyme is ready to bind to the next substrate.