Q BankQuestion BankDocsDocuments

C1.1.13 (HL)—Cyclical and linear pathways in metabolism

Linear pathways move from substrate to final product, while cyclical pathways regenerate intermediates that re-enter the pathway for reuse in metabolism.

Syllabus
First assessment 2025
Objective
C1.1.13
Level
HL

Exam analysis

Chance of appearing2%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper1B
Typical marks1

Common command terms

  • Distinguish

Recent exam appearances

May 2025Paper1B ["HL"] · TZ24(e)[ 1 ]C1.1.13 (HL)—Cyclical and linear pathways in metabolism
May 2023Paper2 ["HL"] · TZ22(b)[ 1 ]C1.1.13 (HL)—Cyclical and linear pathways in metabolism
Practice this objective

Coverage 2023–2025 · Updated 15 Jul 2026

Concept essentials

  • Linear pathways proceed from substrate to final product.
  • Cyclical pathways regenerate a molecule or intermediate.
  • Products can become substrates again in metabolic cycles.
  • The distinction concerns pathway organization, not whether enzymes are involved.
ConceptIB Biology HL