Every type of protein is constructed of a long sequence of amino acids, which are organic compounds made up of carbon, oxygen, and hydrogen atoms. Amino acids are joined together by peptide bonds to form an amino acid chain, called a peptide. When more than 4 amino acids bond together, it is called a polypeptide. These chains can contain hundreds of amino acids. About 20 amino acids (or 22, depending on how they`re categorized) are combined to make proteins in great structural variety. Protein types number in the hundreds of thousands, each with a sequence that is unique in the number, type, order, and shape of amino acids in its chain.
This interactive shows a single amino acid which is joined by peptide bonds to three other amino acids to form a peptide. The peptide then folds and joins with other polypeptide chains to form a protein. Carbon atoms are dark gray, hydrogen atoms are white, nitrogen atoms are blue, radicals are purple, peptide bonds are green, and oxygen atoms are red.