C3.2.3—Blood clotting
Blood clotting explains how a specific barrier, pathogen interaction, immune mechanism or treatment response contributes to protection against infectious disease.
- Syllabus
- First assessment 2025
- Objective
- C3.2.3
- Level
- HL
Exam analysis
Chance of appearing12%of analysed past papers
Latest appearanceMay 2023
Most common paperPaper1
Typical marks1
Common command terms
- Identify
- Describe
- State
- Explain
- Outline
Scoring notes
- Common mistake
- Reversing fibrinogen and fibrin in the clotting sequence.
Recent exam appearances
May 2023Paper1 ["HL"] · TZ121[ 1 ]C3.2.3—Blood clotting
May 2022Paper1 ["HL"] · TZ225[ 1 ]C3.2.3—Blood clotting
May 2022Paper1 ["HL"] · TZ122[ 1 ]C3.2.3—Blood clotting
November 2021Paper1 ["HL"] · TZ020[ 1 ]C3.2.3—Blood clotting
May 2019Paper2 ["HL"] · TZ23(b)[ 3 ]C3.2.3—Blood clotting
Practice this objective
Coverage 2012–2023 · Updated 16 Jul 2026
Concept essentials
- Blood clotting has to be linked to the exact pathogen, cell, molecule or population process involved.
- The biological effect of blood clotting depends on the sequence from trigger to protective outcome.
- Clear distinctions within blood clotting prevent confusion with neighbouring immune responses.
- Evidence for blood clotting is strongest when mechanism and consequence are explained together.