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C1.1.9—Measuring enzyme reactions

Enzyme reactions are measured by tracking product formation or substrate disappearance over time while controlling key experimental variables carefully in investigations.

Syllabus
First assessment 2025
Objective
C1.1.9
Level
HL

Exam analysis

Chance of appearing12%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper3
Typical marks1–2

Common command terms

  • Calculate
  • Suggest
  • Identify
  • Describe
  • Outline
  • Evaluate
  • Deduce
  • Discuss
  • State

Recent exam appearances

May 2025Paper1B ["HL"] · TZ24(d)[ 3 ]C1.1.9—Measuring enzyme reactions
May 2025Paper1B ["HL"] · TZ24(c)[ 2 ]C1.1.9—Measuring enzyme reactions
May 2025Paper1B ["HL"] · TZ24(b)[ 1 ]C1.1.9—Measuring enzyme reactions
May 2025Paper1B ["HL"] · TZ33(c)[ 1 ]C1.1.9—Measuring enzyme reactions
May 2025Paper1B ["HL"] · TZ13(c)[ 1 ]C1.1.9—Measuring enzyme reactions
Practice this objective

Coverage 2013–2025 · Updated 15 Jul 2026

Concept essentials

  • Enzyme activity can be measured through product formation or substrate disappearance.
  • Rate calculations require a measured change over time.
  • Temperature, pH, enzyme concentration and substrate concentration are common controlled variables.
  • Replicates and error bars help judge reliability and variation.
ConceptIB Biology HL