GRE Subject Test: Biochemistry, Cell, and Molecular Biology › Help with Enzyme Mechanics
Which of the following best describes when an inhibitor binds an enzyme at a separate site from the active site, but only when the enzyme and substrate are already bound in complex?
Uncompetitive inhibition
Non-competitive inhibition
Competitive inhibition
Allostery
Reversible inhibition
The correct answer is uncompetitive inhibition. The formation of a enzyme-substrate complex creates an alternative site on the enzyme for an inhibitor to bind. This mechanism is considered uncompetitive because the inhibitor and substrate are not competing for the same binding site on the enzyme.
What is the primary mechanism by how enzymes increase the rate of a reaction?
They lower the activation energy needed in the reaction.
They decrease the internal energy of the final product.
They decrease the stability of the transition state.
They decrease the reverse reaction rate and increase the forward reaction rate.
Enzymes exert their effect on the reaction rate by decreasing the energy needed for the reaction to proceed. As a result, the enzyme will decrease the activation energy. It should be noted that the forward reaction rate and reverse reaction rate are both increased by an enzyme. If this were not the case, more product would be made compared to the uncatalyzed reaction, and enzymes do not affect equilibrium constants for reactions.