Explain why the activity of amylase rapidly decreases above pH 7.

pH 7 is the optimum pH for amylase. This means it performs best and has maximum activity at this pH. Above pH 7, the activity of amylase rapidly decreases beacuse the concentration of H+ ions (or protons) is too low. This change in [H+] alters the interactions between the variable R-groups of the amino acids in the protein chains that make up the enzyme. These interactions include hydrogen bonds, ionic bonds and Van der Waals forces. Their function is to maintain and stabilise the tertiary 3D structure of the proteins of the enzyme, therefore giving the enzyme its specific shape, especially in its active site where its substrate must bind for the reaction to be catalysed. If these stabilising bonds are altered by a change in pH, the shape of the enzyme's active site will also change. This means that the sunstrate is no longer able to bind to the active site and the reaction will not take place, therefore decreasing the activity of amylase.