1. Carbohydrates
Carbohydrates are the most common source of energy used in cellular respiration. Blood glucose must remain constant. Glucose is stored in the muscles as glycogen and used for energy. If not used, carbohydrates are stored as fat.
2. Fats
Unsaturated fats are necessary for cell membrane synthesis. Fats are sources of energy and insulators. Fats also serve as a source for vitamins A, D, E, and K
3. Proteins
Proteins can be stored in the liver and in musce tissue. There is a constant turnover of body protein. Amino acids can build proteins, form nitrogenous bases, can be oxidized for energy, and can be converted into fats and carbohydrates. When amino acids are used, they leave behind a nitrogenous waste which is poisonous and must be removed. Humans can produce 12 of the 20 amino acids. There are 8 amino acids that humans must obtain from food. Brain development requires proteins.
4. Vitamins and Minerals
Vitamins: function in common enzymatic reactions as co-enzymes. There are two types of vitamins: fat soluble and water soluble
5. Mineral
Simple inorganic ions. They may be used in the formation of gross structures, such as bones or may become an active part of functional molecules. Some are necessary for enymatic actions.