Carbon is a versatile element that can form many types of organic molecules important for life. It can bond with up to four other atoms, forming chains and rings. Organic compounds contain carbon bonded to other elements like hydrogen, oxygen, nitrogen and sulfur. The structure and functional groups of organic molecules determine their properties and functions in living things. Important examples are carbohydrates like glucose and fructose, which have the same formula but different structures. Enantiomers are mirror-image isomers that may have different biological effects. Seven key functional groups - hydroxyl, carbonyl, carboxyl, amino, sulfhydryl and phosphate - influence a molecule's polarity, reactivity and other traits. Carbon's properties make