How is structure relevant to enzyme function?

Enzymes are functional proteins which are used to catalyse reactions. They all exhibit primary, secondary and tertiary structure, and some which have more than one polypeptide chain have quaternary structure (such as pyruvate dehydrogenase, an enzyme in the link reaction of respiration). Primary structure involves the sequence of amino acids, and is what determines overall structure due to the different properties of these amino acids (such as if they are acidic, or basic). Secondary structure involves hydrogen bonding between the N=H and C=O bonds of the protien backbone, within the polypeptide sequence, which may form structures such as alpha helices or beta sheets. Tertiary structure involves bonding between the R-groups of amino acid residues in the same polypeptide and is what gives the enyzme it's overall 3D structure (by Van de Waals' forces, hydrogen bonds, hydrophobic interactions, sulphur bonding and ionic bonds). Quaternary structure involves the same types of bonding between residues from different polypeptide chains. Enzymes have specific complementary structures to their substrate which provides specificity. They strain the substrate moving them into the transition state which provides the catalytic properties as they lower the activation energy. This is due to the properties of the residues at the active site and how they interact with the substrate. This is known as the induced fit model. Once the product is formed, they are no longer complementary to the active site of the enzyme and diffuse from the site.