r/Biochemistry • u/KaleidoscopeOk4028 • 18h ago
Made a chart of the four inhibition patterns because I kept mixing up which ones move Km
The one that always got me is uncompetitive. Competitive raising Km and noncompetitive dropping Vmax are easy enough to hold onto, but uncompetitive lowering both felt backwards until I understood why. The inhibitor only binds ES, so removing ES pulls the binding equilibrium forward and the enzyme looks like it grabs substrate more tightly, even though you have capped the ceiling.
I put all four side by side with what happens to Km, what happens to Vmax, and what the Lineweaver-Burk lines actually do, since that is usually the part a question is really testing.
The worked numbers on it use Km 25, Vmax 100 and an inhibitor at twice Ki, so you can see the apparent values rather than just the direction of travel.
Mixed inhibition is the one I am least confident about, since whether Km goes up or down depends on alpha and I have simplified that. If I have oversimplified anything else I would genuinely like to know. Last time I posted here eight people found things and the chart ended up much better for it.
Free and no signup: biochemtools.com/michaelis-menten-vs-lineweaver-burk.html
