Metabolism is the sum of all chemical reactions in the body. It includes both anabolism and catabolism. Anabolism is the process of building up complex molecules from simpler ones, while catabolism is the process of breaking down complex molecules into simpler ones.

Nutrients are the substances that the body needs to grow, repair, and function. There are six major groups of nutrients: water, vitamins, minerals, carbohydrates, lipids, and proteins.

Water is the most important nutrient. It makes up about 60% of the body. Vitamins and minerals are essential for many bodily functions, but they do not provide energy. Carbohydrates, lipids, and proteins are the three major nutrients that provide energy.

Carbohydrates are the main source of energy for the body. They are broken down into glucose, which is the primary fuel for cells. Lipids are also a good source of energy. They are stored in adipose tissue and can be broken down into fatty acids, which can be used to make ATP. Proteins are the building blocks of the body. They are made up of amino acids, which can be used to make enzymes, hormones, and other proteins.