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C1.1.15 (HL)—Competitive inhibition

Competitive inhibitors resemble substrates and occupy active sites, reducing substrate binding until substrate concentration becomes high enough in reactions and pathways.

Syllabus
First assessment 2025
Objective
C1.1.15
Level
HL

Exam analysis

Chance of appearing15%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1
Typical marks1

Common command terms

  • Outline
  • Distinguish
  • Explain

Recent exam appearances

November 2025Paper2 ["HL"] · TZ18(a)[ 4 ]C1.1.15 (HL)—Competitive inhibition
May 2025Paper1A ["HL"] · TZ36[ 1 ]C1.1.15 (HL)—Competitive inhibition
May 2025Paper1B ["HL"] · TZ13(d)[ 1 ]C1.1.15 (HL)—Competitive inhibition
November 2024Paper1 ["HL"] · TZ07[ 1 ]C1.1.15 (HL)—Competitive inhibition
November 2022Paper1 ["HL"] · TZ029[ 1 ]C1.1.15 (HL)—Competitive inhibition
Practice this objective

Coverage 2012–2025 · Updated 15 Jul 2026

Concept essentials

  • Competitive inhibitors bind to enzyme active sites.
  • They often resemble the normal substrate.
  • They reduce enzyme-substrate complex formation and product formation.
  • Higher substrate concentration can reduce their effect.
ConceptIB Biology HL