Advanced Topic 454 of 1102 Kinetics & Equilibrium
Michaelis-Menten Kinetics
Describes enzyme rates as a saturating function of substrate concentration using Vmax and Km.
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In-depth explanation of Michaelis-Menten Kinetics
The Michaelis-Menten model describes enzyme-catalysed reactions in which an enzyme-substrate complex forms reversibly and then breaks down to products. The rate is v = Vmax[S]/(Km + [S]), so it is nearly first order in substrate at low concentration and saturates at Vmax when the enzyme is fully bound at high concentration. Vmax is the maximum rate, reached when all enzyme sites are occupied, and it is proportional to the total enzyme concentration. Km is the substrate concentration at which the rate equals half of Vmax, and it is often used as an inverse measure of the affinity of the enzyme for its substrate.
Going deeper: Michaelis-Menten Kinetics
Key ideas: Mechanism: E + S <-> ES -> E + P, with Km = (k-1 + k2)/k1 and Vmax = k2[E]total. At [S] much less than Km, v is about (Vmax/Km)[S], first order; at [S] much greater than Km, v is about Vmax, zero order. The turnover number kcat equals k2, and catalytic efficiency is kcat/Km, up to 10^8 to 10^9 L per mol per s.
Common mistakes and connections: Students think Km is a dissociation constant for all enzymes, which is true only when k2 is much smaller than k-1, or say Vmax is a constant for an enzyme regardless of its amount. It scales with total enzyme. Another error is stating the rate reaches Vmax at finite concentration; it is only approached asymptotically. Derivation uses the steady state approximation.
Visualization of Michaelis-Menten Kinetics
Rate rises almost linearly with [S] and then saturates at Vmax; Km is the substrate concentration giving half of Vmax (small Km means tight binding). The interactive lesson shows this as a live animation or chart.
Worked example and use case
An enzyme with Km of 2 mM binds its substrate more tightly than one with Km of 20 mM.
Frequently asked questions about Michaelis-Menten Kinetics
What is Michaelis-Menten Kinetics?
Describes enzyme rates as a saturating function of substrate concentration using Vmax and Km.
Is Michaelis-Menten Kinetics a beginner, intermediate or advanced topic?
Michaelis-Menten Kinetics is a advanced topic in Kinetics & Equilibrium. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Michaelis-Menten Kinetics?
Study these earlier topics in Kinetics & Equilibrium first: Homogeneous Catalysis, Heterogeneous Catalysis, Enzyme Catalysis.
What comes after Michaelis-Menten Kinetics?
The next topics in Kinetics & Equilibrium are Lineweaver-Burk Plot and Enzyme Inhibition.
Can I practise Michaelis-Menten Kinetics with quizzes?
Yes. The interactive lesson includes a self-check question on Michaelis-Menten Kinetics, and the Kinetics & Equilibrium quiz draws on every topic in this area.
Where Michaelis-Menten Kinetics fits in Kinetics & Equilibrium
Michaelis-Menten Kinetics is topic 35 of 91 in Kinetics & Equilibrium.