Enzymes are proteins that reduce the amount of energy it takes for a chemical reaction to take place.
Different chemical reactions require different amounts of energy in order to occur. The amount of energy needed for a chemical reaction to occur is called the activation energy.
The molecules enzymes bind to are called substrates. The shape of an enzyme is specific to the type of substrate that it binds with. The part of an enzyme that binds with the substrate is known as the active site.
Enzymes are used in the human body to speed up the digestion of food. There are enzymes in the body that break down starches, milk products, and proteins. When enzymes help to break down food, it can be more quickly converted into energy and raw materials that can be used in the body.