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C1.2.12 (HL)—Krebs cycle

The Krebs cycle oxidizes acetyl groups in the matrix, releasing carbon dioxide and producing ATP plus reduced carriers, supporting usable cellular work and measurable biological activity.

Syllabus
First assessment 2025
Objective
C1.2.12
Level
HL

Exam analysis

Chance of appearing8%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1
Typical marks1

Common command terms

  • Explain
  • Identify
  • Outline

Recent exam appearances

November 2025Paper1A ["HL"] · TZ17[ 1 ]C1.2.12 (HL)—Krebs cycle
November 2024Paper1 ["HL"] · TZ029[ 1 ]C1.2.12 (HL)—Krebs cycle
November 2023Paper1 ["HL"] · TZ225[ 1 ]C1.2.12 (HL)—Krebs cycle
November 2020Paper1 ["HL"] · TZ031[ 1 ]C1.2.12 (HL)—Krebs cycle
May 2019Paper1 ["HL"] · TZ215[ 1 ]C1.2.12 (HL)—Krebs cycle
Practice this objective

Coverage 2012–2025 · Updated 15 Jul 2026

Concept essentials

  • The Krebs cycle occurs in the mitochondrial matrix.
  • Acetyl groups join oxaloacetate to form a six-carbon compound.
  • Two decarboxylation reactions release carbon dioxide.
  • The cycle produces ATP, reduced NAD and reduced FAD while regenerating oxaloacetate.
ConceptIB Biology HL