Enzymes Enzymes are proteins that work together in a cellular metabolic reaction, they catalyze the reaction. Even though, it is involved in a chemical reaction it returns back to its original state and prepares for its next chemical reaction. Enzymes come in many different shapes, the shape of enzyme provides a certain shape for the substrate to fit into, similar to a lock and key. When these two shapes connect to one and another a chemical reaction is then catalyzed by the enzyme and a reaction takes place in the substrate. The reacted substrate breaks off, leaving the enzyme back to its original state and ready to repeat the process again . Enzymes that work inside the cell are called intracellular. Enzymes that work outside the