C3.1.20 (HL)—Auxin efflux carriers
Auxin efflux carriers links named stimuli, coordinating structures and effectors so body systems or plant tissues produce an integrated biological response.
- Syllabus
- First assessment 2025
- Objective
- C3.1.20
- Level
- HL
Exam analysis
Chance of appearing3%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper2
Typical marks1–2
Common command terms
- Analyse
- Compare
- Contrast
- Deduce
- Identify
Scoring notes
- Common mistake
- Treating low oxygen as the only trigger and omitting carbon-dioxide-driven pH change.
Recent exam appearances
November 2025Paper1A ["HL"] · TZ127[ 1 ]C3.1.20 (HL)—Auxin efflux carriers
May 2025Paper1A ["HL"] · TZ329[ 1 ]C3.1.20 (HL)—Auxin efflux carriers
May 2017Paper2 ["HL"] · TZ21(d)(ii)[ 2 ]C3.1.20 (HL)—Auxin efflux carriers
May 2017Paper2 ["HL"] · TZ21(d)(i)[ 2 ]C3.1.20 (HL)—Auxin efflux carriers
May 2017Paper2 ["HL"] · TZ21(c)[ 2 ]C3.1.20 (HL)—Auxin efflux carriers
Practice this objective
Coverage 2017–2025 · Updated 16 Jul 2026
Concept essentials
- Auxin efflux carriers depends on linking the stimulus to the coordinating structure or signal.
- The pathway for auxin efflux carriers must keep information flow and response direction clear.
- Named tissues, hormones, neurons or effectors give auxin efflux carriers its biological specificity.
- Evidence about auxin efflux carriers is strongest when structure, mechanism and outcome are connected.