Amino Acid
The
basic building blocks of proteins. Living things contain 20 amino acids:
alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid,
glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine,
phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine.