Features of Enzyme Catalyzed Reactions Enzymes are biological catalysts. Catalysts lower the activation energy for reactions. The lower the activation energy for a reaction, the faster the rate. Thus enzymes speed up reactions by lowering activation energy. Many enzymes change shape when substrates bind.
Enzymes have active sites.
The enzyme active site is the location on the enzyme surface where substrates bind, and where the chemical reaction catalyzed by the enzyme occurs. Enzymes form complexes with their substrates. Keq depends only on the difference in energy level between reactants and products. Change DG for a reaction. As shown in the graphs above, enzymes only lower activation energy, but do not change the difference in energy levels between reactants and products.