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C1.2.15 (HL)—Chemiosmosis

Chemiosmosis uses proton flow through ATP synthase to couple the proton gradient to ATP production, supporting usable cellular work and measurable biological activity.

Syllabus
First assessment 2025
Objective
C1.2.15
Level
HL

Exam analysis

Chance of appearing6%of analysed past papers
Latest appearanceMay 2024
Most common paperPaper1
Typical marks1–7

Common command terms

  • Explain
  • Identify

Recent exam appearances

May 2024Paper1 ["HL"] · TZ132[ 1 ]C1.2.15 (HL)—Chemiosmosis
May 2022Paper2 ["HL"] · TZ17(c)[ 7 ]C1.2.15 (HL)—Chemiosmosis
November 2020Paper2 ["HL"] · TZ03(b)[ 4 ]C1.2.15 (HL)—Chemiosmosis
November 2018Paper1 ["HL"] · TZ029[ 1 ]C1.2.15 (HL)—Chemiosmosis
May 2017Paper2 ["HL"] · TZ15(a)[ 8 ]C1.2.15 (HL)—Chemiosmosis
Practice this objective

Coverage 2012–2024 · Updated 15 Jul 2026

Concept essentials

  • Electron transport pumps protons into the intermembrane space.
  • Protons flow back to the matrix through ATP synthase.
  • ATP synthase couples proton flow to ADP phosphorylation.
  • Chemiosmosis occurs in mitochondrial cristae and thylakoid membranes.
ConceptIB Biology HL