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C1.2.7 (HL)—NAD as hydrogen carrier

NAD accepts hydrogen during oxidation reactions and carries high-energy electrons to later respiration stages, supporting usable cellular work and measurable biological activity.

Syllabus
First assessment 2025
Objective
C1.2.7
Level
HL

Exam analysis

Chance of appearing3%of analysed past papers
Latest appearanceMay 2023
Most common paperPaper1
Typical marks1

Common command terms

  • Identify

Recent exam appearances

May 2023Paper1 ["HL"] · TZ129[ 1 ]C1.2.7 (HL)—NAD as hydrogen carrier
May 2016Paper3 ["HL"] · TZ09(a)[ 1 ]C1.2.7 (HL)—NAD as hydrogen carrier
May 2014Paper1 ["HL"] · TZ231[ 1 ]C1.2.7 (HL)—NAD as hydrogen carrier
Practice this objective

Coverage 2014–2023 · Updated 15 Jul 2026

Concept essentials

  • NAD is reduced when it accepts hydrogen or electrons.
  • Reduced NAD carries energy from oxidation reactions.
  • Reduced NAD can donate electrons to the electron transport chain.
  • NAD links substrate oxidation to later ATP production.
ConceptIB Biology HL