Physiology Quiz - Michaelis-Menten Kinetics - Part 2

Michaelis-Menten kinetics is used to describe the rate of a reaction catalyzed by an enzyme as a function of the substrate concentration. This type of analysis is also commonly used to describe the rate of transporter-mediated translocation of ions and molecules across biological membranes. Test your basic knowledge of Michaelis-Menten kinetics by taking this simple quiz.

(1) A higher numerical value of the Michaelis constant (K_{m}) indicates a lower enzyme/transporter affinity for its substrate.

(2) The figure below shows the reaction velocity catalyzed by an enzyme as a function of the enzyme substrate concentration. Such a relationship is typically referred to as a dose-response relationship. Based on the data shown, what is the K_{m} (Michaelis constant) of this enzyme for its substrate? Note that the reaction velocity is normalized to the maximum velocity (V_{max}). Therefore, in the plot shown, V_{max} = 100%.

(3) Assume that the reaction catalyzed by an enzyme follows Michaelis-Menten kinetics. The substrate concentration (K_{m}, Michaelis constant) needed to reach 50% of the maximum reaction velocity (V_{max}) is 25 μM. What substrate concentration is required to obtain at least 50% of the maximum reaction velocity?

(4) The Michaelis-Menten equation represents a special case of the Hill equation, where the Hill coefficient has been set to one.

(5) Assume that the reaction catalyzed by an enzyme follows Michaelis-Menten kinetics. If at a substrate concentration of 100 nM, the reaction proceeds at 50% of the maximum reaction velocity (V_{max}), what is the Michaelis constant (K_{m}) for this substrate. K_{m} is the substrate concentration needed to reach 50% of V_{max}.