1) E____, the catalysts of biological systems, are remarkable molecular devices that determine the patterns of chemical transformations. They also mediate the transformation of one form of energy into another. The most striking characteristics of enzymes are their 2) c____ power and specificity. Catalysis takes place at a particular site on the enzyme called the 3) a____ site. Nearly all known enzymes are 4) p____. However, proteins do not have an absolute monopoly on 5) c____; the discovery of catalytically active RNA molecules provides compelling evidence that RNA was an early biocatalyst. Proteins as a class of macromolecules are highly effective catalysts for an enormous diversity of chemical 6) r____ because of their capacity to specifically bind a very wide range of molecules. By utilizing the full repertoire of intermolecular forces, enzymes bring 7) s____ together in an optimal orientation, the prelude to making and breaking chemical 8) b____. They 9) c____ reactions by stabilizing transition states, the highest-energy species in reaction pathways.