D2.1.15 (HL)—Cell cycle control by cyclins
Cyclins control cell-cycle timing by rising and falling, activating CDKs that phosphorylate proteins at specific stages of division in cells.
- Syllabus
- First assessment 2025
- Objective
- D2.1.15
- Level
- HL
Exam analysis
Chance of appearing4%of analysed past papers
Latest appearanceMay 2022
Most common paperPaper1
Typical marks1–4
Common command terms
- Compare
- Explain
- State
Scoring notes
- Common mistake
- Saying cyclins are constant instead of rising and falling during stages.
Recent exam appearances
May 2022Paper2 ["HL"] · TZ22(a)(iii)[ 1 ]D2.1.15 (HL)—Cell cycle control by cyclins
May 2018Paper1 ["HL"] · TZ14[ 1 ]D2.1.15 (HL)—Cell cycle control by cyclins
May 2017Paper1 ["HL"] · TZ14[ 1 ]D2.1.15 (HL)—Cell cycle control by cyclins
November 2016Paper2 ["HL"] · TZ02(b)[ 4 ]D2.1.15 (HL)—Cell cycle control by cyclins
Practice this objective
Coverage 2016–2022 · Updated 16 Jul 2026
Concept essentials
- Cyclin concentrations fluctuate through the cell cycle.
- Cyclins activate cyclin-dependent kinases.
- CDK-cyclin complexes phosphorylate proteins that drive cell-cycle events.
- Different cyclins regulate different stages or checkpoints.