Medical Definition of Amino acidAmino acid: One of the20 building blocks from which proteins are assembled. Isoleucine, leucine, lysine, phenylalanine, threonine, tryptophan, and valine are deemed 'essential' amino acids because the human body cannot make them and they must be obtained in the diet. Amino acids are sometimes taken orally in supplement form. Last Editorial Review: 5/13/2016 Back to MedTerms online medical dictionary A-Z List Need help identifying pills and medications? |


