A molecule is composed of chains of amino acids. This sequence of the amino acids determines the shape and the function of the molecule. Identify the molecule.

A protein molecule is made from a long chain of these amino acids, each linked to its neighbor through a covalent peptide bond (Figure 3-1). Proteins are therefore also known as polypeptides. Each type of protein has a unique sequence of amino acids, exactly the same from one molecule to the next.