Why are proteins considered polymers?

Proteins are considered polymers because they are formed by the polymerization of amino acids, and therefore amino acids are monomers of proteins and peptides. In a protein molecule, amino acids are held together through peptide bonds. Amino acids are also called the “building blocks” of proteins. Although there are about 300 amino acids in nature, only 20 amino acids are commonly found in human and other mammalian proteins. These amino acids are known as “standard amino acids” or “proteinaceous amino acids”.