How do enzymes work?

For a reaction to occur successfully, two or more molecules must collide with the right orientation and a sufficient amount of activation energy. Activation energy is the energy that the molecules need to trigger a chemical reaction between them. Enzymes are biological catalysts that possess an active site. The active site is a part of an enzyme molecule with a specific shape that fits perfectly with a reactant molecule in the same manner in which a key fits into a lock. The molecule that binds to the enzyme is called the substrate group. Enzymes work by binding to reactant molecules and holding them in a way that allows the chemical bond-breaking and bond-forming processes to occur more easily without the need for large amounts of activation energy.