C6H12O6 is the chemical formula of several simple sugars, the three most notable of which are glucose, fructose and galactose. Other sugars have the same chemical formula but are rare or not found in nature. While these sugars have the same number of atoms, their molecules are configured differently.
Glucose is the most fundamental source of energy for living organisms on Earth. It is burned to turn ammonium diphosphate into ammonium triphosphate, a vital energy source for cells. Several glucose molecules linked together can take the form of starch or cellulose. Human beings have enzymes that separate the glucose molecules in starch, but humans cannot turn cellulose into usable energy.
Fructose, also known as fruit sugar, is the sweetest of all sugars and is found in honey. When glucose and fructose are bound together, they form sucrose, or table sugar. Fructose is used by the food industry in the creation of high-fructose corn syrup, which contains a roughly one-to-one ratio of glucose and fructose. Unlike sucrose, this syrup can be dissolved in acidic foods without deteriorating.
Galactose also has the formula C6H12O6. Mammals convert glucose into galactose, then they bind galactose and glucose together to form lactose, which is the sugar in milk.