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C1.1.7—Relationships between structure and function

Enzyme function depends on active-site structure, chemical attraction and tertiary shape that allow only suitable substrates to bind effectively during catalysis.

Syllabus
First assessment 2025
Objective
C1.1.7
Level
SL

Exam analysis

Chance of appearing1%of analysed past papers
Latest appearanceMay 2018
Most common paperPaper2
Typical marks3–6

Common command terms

  • Explain

Recent exam appearances

May 2018Paper2 ["SL"] · TZ24(b)[ 3 ]C1.1.7—Relationships between structure and function
November 2013Paper2 ["SL"] · TZ07(b)[ 6 ]C1.1.7—Relationships between structure and function

Coverage 2013–2018 · Updated 15 Jul 2026

Specificity Depends on a Fold That Can Be Lost

An enzyme is specific because the active site's three-dimensional arrangement of shape, charge and chemical groups permits productive binding of only particular substrate molecules.

High temperature or extreme pH can disrupt hydrogen bonds, ionic interactions and other weak forces that maintain tertiary structure. The active site changes shape or charge, so the substrate no longer binds productively: the enzyme is denatured.

Denaturation does not normally hydrolyse the peptide bonds of the primary structure. Moderate pH effects may be reversible when the original bonding pattern reforms; severe heating commonly causes irreversible aggregation or misfolding.

SL Checkpoint: Explain the Curve, Not Just Its Shape

globular fold → active-site chemistry → induced fit → lower activation energy → faster turnover → controlled metabolic pathways

When explaining a rate pattern, identify what changed, then connect it to:

  • molecular motion and successful collisions
  • active-site occupancy
  • active-site shape and charge
  • depletion or changing conditions during measurement

A strong investigation measures initial rate, changes one independent variable, controls alternatives, includes a relevant control and uses repeats to reveal variation.

Relationships between structure and function

[ 6 ]

Some proteins in membranes act as enzymes. Outline enzyme-substrate specificity.

Concept essentials

  • Active-site structure determines which substrates can bind.
  • Specificity depends on shape and chemical properties.
  • Denaturation changes tertiary structure and active-site function.
  • Enzyme-substrate complex formation depends on structural compatibility.