Enzymes Practice Test

Initial reaction rates are measured at multiple substrate concentrations for an enzyme with and without Inhibitor Z. With Z present, the maximum rate observed at very high substrate concentration is lower than without Z, and increasing substrate does not restore the original maximum. Enzyme concentration, pH, and temperature are constant. Which explanation best accounts for Inhibitor Z’s effect?​

A student measures initial rates for an enzyme at a fixed enzyme concentration while varying substrate concentration. When substrate is increased from 0.2 mM to 0.4 mM, the rate approximately doubles. When substrate is increased from 5 mM to 10 mM, the rate changes very little. The enzyme remains stable and no inhibitor is present. Which inference is most consistent with these observations?