3D Competitive Inhibition Simulation

Reaction rate17.1 µM/s

Apparent Km100.0 µM

Inhibitor bound38%

Product0.0 µM

Substrate and inhibitor compete for one active site

Competitive-inhibition laboratory

Mission: watch substrate and inhibitor race for the same active site, then change their concentrations to control the winner.

Experiment

Substrate concentration, [S]40 µM

Enzyme concentration, [E]1.0 µM

Km40 µM

Inhibitor constant, Ki30 µM

Competitive inhibitor, [I]0 µM

Simulation speed1×

Live measurements

Reaction rate17.1 µM/s

Apparent Km100.0 µM

Inhibitor-bound sites38%

Product formed0.0 µM

Substrate and inhibitor compete for the same pocket. More inhibitor lowers the observed rate by occupying sites without making product.

Competitive-inhibition curves

With inhibitorNo inhibitor◆ Current measurement

Microscope & camera

Focus: noneTap a structure

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Tap an active site, substrate, inhibitor, blocked complex, or product for a compact molecular view. Drag empty space to pan.

Teacher / Demo tools

Interactive competitive-inhibition lecture

The lesson starts immediately. Each narrated point changes the molecules, arrows, graph, and microscopic view before the next point begins.

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Ready for competitive inhibition

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Learning objectives

Identify substrate and competitive inhibitor as rivals for the same active site.
Relate concentration and Ki to the probability of active-site occupancy.
Explain why apparent Km rises while ideal Vmax remains unchanged.
Predict when extra substrate can rescue reaction rate.
Connect competitive inhibition to drug action and metabolic control.

Key concepts

A competitive inhibitor reversibly occupies the enzyme active site without becoming product. In the simplified model, apparent Km = Km × (1 + [I] ÷ Ki), while Vmax remains unchanged. The rate is v₀ = Vmax × [S] ÷ (apparent Km + [S]). Molecular sizes and time are conceptually scaled.

Suggested experiments

Set inhibitor to zero and observe normal substrate binding.
Keep substrate fixed while raising inhibitor concentration.
Use a low Ki to model a more potent inhibitor.
Raise substrate greatly and watch it outcompete a reversible inhibitor.
Compare equal substrate and inhibitor concentrations at different Km and Ki values.

Questions for exploration

Why does inhibitor binding produce no product?
Why does the inhibited curve shift right rather than lowering its final plateau?
Which matters more for competition: concentration or binding strength?

Applications and misconceptions

Competitive inhibition is used in medicines, pathway regulation, toxicology, and enzyme assays. A competitive inhibitor does not permanently destroy the enzyme, and increasing substrate can overcome ideal reversible competition. A lower Ki means stronger inhibition, not a faster reaction.

Competitive-inhibition challenge

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