Physiology Quiz: Michaelis-Menten Kinetics - Part 2

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.

	True
	False

(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%.

	(A) 2.5 nM
	(B) 5.0 nM
	(C) 10.0 nM
	(D) 20.0 nM
	(E) 25.0 nM

(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?

	(A) 25 μM
	(B) 50 μM
	(C) 100 μM
	(D) 250 μM
	(E) 475 μM

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

	True
	False

(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.

	(A) 25 nM
	(B) 50 nM
	(C) 100 nM
	(D) 150 nM
	(E) 200 nM