Chymotrypsin, trypsin, and elastase are digestive enzymes called serine proteases. the serine proteases differ in substrate specificity: chymotrypsin cleaves peptide bonds after aromatic or bulky hydrophobic side chains; trypsin requires basic amino acid residues; and elastase cleaves bonds following small uncharged side chains. a chart of amino acids can be found here. the specificity pockets (substrate-binding sites) of each of the serine proteases are drawn below.

Liquid ammonia is produced at high temperatures and under great pressure in a tank by passing a mixture of nitrogen gas and hydrogen gas over an iron catalyst. the reaction is represented by the following equation. n2(g) + 3h2(g) → 2nh3(g) changing all but one experimental condition will affect the amount of ammonia produced. that condition is a) increasing the concentration of both reactants b) changing the temperature within the tank c) decreasing the pressure within the tank. d) increasing only the amount of nitrogen present.