28.

The rate of an enzyme-catalyzed reaction increases 250% as the substrate concentration is raised from 0.05 Km to 0.2 Km. However the rate increases only 14% as the substrate concentration is raised from 5Km to 20Km because

• a. high substrate concentrations inhibit enzymes.
• b. all enzymes are allosteric.
• c. when the substrate reaches 5Km, the active site is mostly saturated.
• d. when the enzyme becomes saturated, the rate of catalysis decreases.
• e. substrates act as uncompetitive inhibitors.