Competitive inhibitors resemble substrates and occupy active sites, reducing substrate binding until substrate concentration becomes high enough in reactions and pathways.
Coverage 2012–2025 · Updated 15 Jul 2026
A competitive inhibitor binds reversibly to the enzyme's active site and prevents substrate binding while it occupies that site.
The inhibitor often resembles part of the substrate. Increasing substrate concentration raises the chance that substrate rather than inhibitor occupies the active site, so the inhibition can be reduced.
Statins competitively inhibit an active site in the cholesterol-synthesis pathway, reducing pathway flux. In the ideal kinetic model, more substrate raises the apparent substrate requirement while the original maximum rate remains reachable.
If a reaction recovers its uninhibited maximum rate at sufficiently high substrate concentration, reversible active-site competition is a plausible mechanism.
Competitive inhibition does not permanently destroy enzyme. Contrast it with reversible allosteric inhibition, whose effect is not overcome simply by adding substrate.
This objective is assessed through structured response, commonly using Outline / Distinguish / Explain.
Outline / Distinguish / Explain
Build the answer around this relationship: Competitive inhibitors bind to enzyme active sites.
Representative question
Explain, using an example, how competitive inhibitors interfere with enzyme activity.
Enzymes can act inside or outside cells, metabolic reactions release heat, pathways may be linear or cyclical, and pathway output is regulated by inhibition. Competitive inhibitors bind active sites and can be overcome by more substrate; non-competitive inhibitors bind allosteric sites; feedback inhibition uses end products to inhibit earlier enzymes; mechanism-based inhibitors trap enzymes after reaction begins.
