Metabolism is a series of complex processes by which the human body converts food, water, and oxygen into tissue, energy, and waste products. It is a continuous process and goes on in every cell of the body. It comprises the breaking down of substances into simpler parts, and their shuffling and recombination into countless new substances that compose the body. For example, the carbohydrates are broken down by enzymes and acids and converted into pure sugar or glucose. The constructive chemical and physical process by which food materials are adapted for the use of the body is known as anabolism; and the destructive process by which energy is produced with the breaking down of tissues into waste products is called catabolism. The two processes together are called metabolism.