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B1.2.11 (HL)—Quaternary structure

Quaternary structure forms when multiple polypeptide chains or associated groups combine into one functional protein complex or subunit assembly structurally.

Syllabus
First assessment 2025
Objective
B1.2.11
Level
HL

Exam analysis

Chance of appearing3%of analysed past papers
Latest appearanceMay 2024
Most common paperPaper1
Typical marks1

Common command terms

  • Define
  • State
  • Identify

Recent exam appearances

May 2024Paper1 ["HL"] · TZ16[ 1 ]B1.2.11 (HL)—Quaternary structure
May 2022Paper2 ["HL"] · TZ14(a)[ 1 ]B1.2.11 (HL)—Quaternary structure
November 2021Paper1 ["HL"] · TZ06[ 1 ]B1.2.11 (HL)—Quaternary structure
Practice this objective

Coverage 2021–2024 · Updated 15 Jul 2026

Concept essentials

  • Quaternary structure involves two or more polypeptide chains in one protein.
  • Haemoglobin has quaternary structure because it contains multiple globin chains.
  • Insulin has two polypeptide chains stabilized by disulfide bridges.
  • A single polypeptide can have tertiary structure without quaternary structure.
ConceptIB Biology HL