molecule - (physics and chemistry) the simplest structural unit of an element or compound

organic compound - any compound of carbon and another element or a radical

protein - any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes; "a diet high in protein"

carbohydrate, saccharide, sugar - an essential structural component of living cells and source of energy for animals; includes simple sugars with small molecules as well as macromolecular substances; are classified according to the number of monosaccharide groups they contain

lipid, lipide, lipoid - an oily organic compound insoluble in water but soluble in organic solvents; essential structural component of living cells (along with proteins and carbohydrates)

nucleic acid - (biochemistry) any of various macromolecules composed of nucleotid chains that are vital constituents of all living cells