Summary
Models reaction velocity as Vmax times substrate over Km plus substrate, describing enzyme saturation.
In depth
The equation v = Vmax[S]/(Km + [S]) gives a hyperbolic curve. Km is the substrate concentration giving half-maximum rate and reflects affinity: low Km means high affinity. Vmax is reached when all active sites are occupied.
Lineweaver-Burk plots (1/v against 1/[S]) linearise data to extract Km and Vmax and diagnose inhibition type.
At low substrate concentration, rate is nearly proportional to [S], while at high concentration it levels off at Vmax. Km is independent of enzyme amount, but Vmax depends on it. The kcat, or turnover number, equals Vmax divided by total enzyme concentration.
Lineweaver-Burk plots turn the hyperbola into a straight line (1/v against 1/[S]), which makes it easier to identify types of inhibition, although modern analyses fit the curve directly. Hexokinase has a low Km for glucose, while glucokinase has a high Km, so liver only takes up glucose when levels are high.
Remember: Km is a concentration, not a rate, and a lower value means higher affinity.
Frequently asked questions
What is Michaelis-Menten Kinetics?
Models reaction velocity as Vmax times substrate over Km plus substrate, describing enzyme saturation.
Which area of biology covers Michaelis-Menten Kinetics, and how advanced is it?
Michaelis-Menten Kinetics is one of the 51 topics in Biomolecules & Biochemistry. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Cooperativity, Noncompetitive Inhibition, Competitive Inhibition.
Can you give an example of Michaelis-Menten Kinetics?
A competitive inhibitor increases Km but not Vmax; a noncompetitive one lowers Vmax.
What should I learn before Michaelis-Menten Kinetics?
Work through the Beginner topics in Biomolecules & Biochemistry first, such as Water Properties, Carbon Chemistry, Carbohydrates, then return to Michaelis-Menten Kinetics. Advanced topics assume the Intermediate vocabulary.
What topics are related to Michaelis-Menten Kinetics?
The closest topics to Michaelis-Menten Kinetics are Cooperativity, Noncompetitive Inhibition, Competitive Inhibition, Factors Affecting Enzymes. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Michaelis-Menten Kinetics?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Michaelis-Menten Kinetics. To practise the whole of Biomolecules & Biochemistry, use the Biomolecules & Biochemistry quiz.
How is Michaelis-Menten Kinetics different from Cooperativity?
Michaelis-Menten Kinetics: Models reaction velocity as Vmax times substrate over Km plus substrate, describing enzyme saturation. Cooperativity: Binding of a ligand to one subunit alters affinity at others, giving haemoglobin its sigmoidal oxygen curve. Read both side by side and note what each one explains.
How should I study Michaelis-Menten Kinetics step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Cooperativity and explain the difference aloud. Finally, take the Biomolecules & Biochemistry quiz and come back to this page for any question you miss.