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Which O-Level Pure Biology topics come up most often?
We counted every question in 18 O-Level Pure Biology papers in Rae's library: 485 questions across 19 topics. The most common single topic is Enzyme action and factors affecting reaction rate, at 14.8% of all questions.
Every topic, ranked
| Topic | Questions | Share | Papers | Avg marks |
|---|---|---|---|---|
| Enzyme action and factors affecting reaction rate | 72 | 14.8% | 16 | 1.9 |
| Human digestion, absorption and liver functions | 64 | 13.2% | 11 | 2.0 |
| Cell structure, organelles and specialised cells | 60 | 12.4% | 15 | 1.7 |
| Diffusion, osmosis and active transport | 60 | 12.4% | 11 | 1.6 |
| Blood, blood vessels, heart and cardiac cycle | 36 | 7.4% | 9 | 2.0 |
| Carbohydrates, fats, proteins and food tests | 35 | 7.2% | 13 | 1.7 |
| Transpiration and water transport in plants | 27 | 5.6% | 8 | 2.2 |
| Photosynthesis and limiting factors | 26 | 5.4% | 7 | 2.1 |
| Gas exchange and aerobic/anaerobic respiration | 26 | 5.4% | 9 | 2.3 |
| DNA structure and gene-to-protein basics | 17 | 3.5% | 5 | 2.8 |
| Leaf, stem and root structure in plants | 15 | 3.1% | 7 | 1.5 |
| Monohybrid inheritance, mutation and natural selection | 13 | 2.7% | 4 | 2.1 |
| Infectious disease causes, spread and control | 8 | 1.6% | 4 | 1.5 |
| Kidney structure, excretion and dialysis | 7 | 1.4% | 4 | 3.2 |
| Coronary heart disease causes and prevention | 6 | 1.2% | 6 | 2.6 |
| Translocation of food in phloem | 5 | 1.0% | 4 | 1.0 |
| Hormonal coordination and diabetes | 4 | 0.8% | 4 | 1.5 |
| Nervous system, reflex arc and the eye | 3 | 0.6% | 3 | 3.7 |
| Effects of smoking on respiratory health | 1 | 0.2% | 1 | - |
How to use this
Topic frequency is a guide to where revision time pays back, not a prediction. The three topics that appear most here (Enzyme action and factors affecting reaction rate, Human digestion, absorption and liver functions, Cell structure, organelles and specialised cells) are worth being fluent in, but a topic near the bottom of the table can still carry a whole question in any given year.
Method, and what this is not
These counts come from real O-Level Pure Biology papers held in Rae's library (papers dated 2019 to 2024), which include school preliminary papers as well as national papers. Each question is labelled with one topic. This is a count of what our library contains, not an official SEAB distribution, and it does not tell you what will be set in a future exam. Questions that could not be labelled with a single topic are excluded from the counts.
You are welcome to cite or link to this page. If you would like the underlying counts in another format, get in touch through the O-Level Pure Biology page.