Macronutrients, minerals, vitamins and energy

Carbohydrates have the general formula C-n(H2O)(n). Monosaccharides have between three and six carbon atoms and exist as chains or ring structures. As rings, they link with other monosaccharide rings. The major carbohydrate in humans is glucose, which is stored as glycogen: branching chains of glucose molecules. Fat (triglyceride), which makes up adipose tissue, consists of three fatty acids bonded to glycerol, but other lipids include phospholipids and steroids. Proteins are composed of chains of amino acids linked by amide bonds folded on each other to form protein structures. Vitamins and minerals are obtained from the diet and are required in varying quantities for a variety of metabolic processes. Energy is derived from the oxidation of carbohydrate, fat and protein. Energy expenditure and substrate oxidation can be calculated from oxygen consumption, carbon dioxide production and urinary nitrogen excretion.