Proteins are the indispensable agents of biological function, and amino acids are the building blocks of proteins.The stunning diversity of the thousands of proteins found in nature arises from the intrinsic properties of only 20 commonly occurring amino acids.Proteins are the indispensable agents of biological function, and amino acids are the building blocks of proteins. The stunning diversity of the thousands of proteins found in nature arises from the intrinsic properties of only 20 commonly occurring amino acids