Which increase buys more?
Compare S = 1 → 4 with S = 4 → 16. Both changes multiply substrate by four. Why do their uninhibited rate increases differ?
Enzymes / Saturation & regulation
More substrate.
Same enzyme.
See where the initial rate levels off—and when extra substrate can reduce an inhibitor’s fractional effect.
Same inputs. Compare the rates.
- Uninhibited · circle
- Competitive · square
- Pure noncompetitive · triangle
With inhibitor ratio 0, all three curves and markers overlap.
| Model | Initial rate product units/min | Of uninhibited rate | Limiting rate product units/min | Apparent Km concentration units |
|---|---|---|---|---|
| Uninhibited | — | — | — | — |
| Competitive | — | — | — | — |
| Pure noncompetitive | — | — | — | — |
Values are displayed to five significant figures. The CSV retains unrounded calculated values. Scroll the table sideways if its columns do not fit.
At zero substrate, “of uninhibited rate” is undefined because both rates are zero. Its CSV cell is empty.
Enter valid values to compare.
The graph, table and comparison download will return when both inputs are within their shown ranges. The unchanged course deck remains available below.
From the existing lesson
Recreate the saturation example.
These buttons change substrate only. Compare the uninhibited rates with question enz-binding-2, which rounds to one decimal.
Can the fractional loss shrink?
Keep inhibitor ratio 3. Move from S = 1 to S = 16 and follow the competitive percentage in the table. Predict what happens as substrate becomes very abundant.
What stays proportional?
With the same nonzero inhibitor ratio, follow the pure noncompetitive percentage as you vary positive substrate. Separate a rising rate from recovery of the original limiting rate.
Continue in RecallWeave
Enzymes: energy, speed and control
Download the existing twelve-question deck, then use Bring your own lesson → Choose a deck file in RecallWeave and explicitly start the selected deck. Read the worked course or this explorer’s model guide.
What the curves mean
These are fictional initial-rate calculations for a simple, reversible inhibition model: fixed enzyme amount, fixed temperature and pH, negligible substrate depletion and product accumulation during the initial-rate measurement, and inhibition already equilibrated. The curves do not describe reaction progress over time.
Pure noncompetitive is the equal-inhibition-constant special case. It is an extension for comparison, not a kinetic label inferred from the course’s allosteric-binding example. Binding at a separate site alone does not identify a rate law.
No cooperativity, substrate inhibition, irreversible or slow-binding inhibition, pathway feedback dynamics, or equilibrium composition is calculated.
Read the model
Equations and parameter meanings
Let S be substrate concentration and r = I/Ki. With Vmax = 10 and Km = 1:
Uninhibited: v = 10 S / (1 + S)
Competitive: v = 10 S / (1 + r + S)
Pure noncompetitive: v = (10 / (1 + r)) S / (1 + S)
Km is the concentration giving half the limiting rate in a Michaelis–Menten curve; it is not generally a binding-equilibrium constant. The listed values use the fictional units shown above.
Primary references: IUBMB, enzyme kinetics §§4.1–4.2 and 6.2–6.4, for rate terminology and the precise inhibition distinction; OpenStax, Biology 2e §6.5, for the course’s biological context. The page, graph and examples are original.
Local calculation and interaction checks establish software behavior. No measured learning benefit is claimed.