Differentiate between the four different levels of protein structure.

The primary structure of a protein is the sequential order of the amino acids. The particular sequence of amino acids determines the interaction between side chains. It is these interactions that determine way the amino acid chain folds and, therefore, the secondary structure. The stability of the secondary structure is achieved through the bonding of hydrogen atoms or sulphur atoms, which creates a bridge between two protein strands or two parts of the same strand of protein. The spiral of the secondary structure further folds into a unique three-dimensional shape, referred to as the protein's tertiary structure; this structure is critically important because it determines each protein's function in the body. Often, two or more separate polypeptides bond to form an even larger protein with a quaternary structure, which may be globular or fibrous.