Biochemistry peptide bonding between amino acids

In 1953, Frederick Sanger determined the amino acid sequence of insulin, a protein hormone (Figure 3.22). This work is a landmark in biochemistry because it showed for the first time that a protein has a precisely defined amino acid sequence. Moreover, it demonstrated that insulin consists only of L amino acids linked by peptide bonds between a-amino and a-carboxyl groups. This accomplishment stimulated other scientists to carry out sequence studies of a wide variety of proteins. Indeed, the complete amino acid sequences of more than 100,000 proteins are now known. The striking fact is that each protein has a unique, precisely defined amino acid sequence. The amino acid sequence of a protein is often referred to as its primary structure. 

Amides are notable for their role in biochemistry, i.e., the special amide bond between two amino acids is called a peptide bond. 

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