S: (n) 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"
S: (n) catalyst, accelerator ((chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected)