CIE IGCSE Biology Predicted Topics for 2026 Exams
What if you knew which topics were most likely to appear before you even opened the paper? That is not guessing. That is pattern recognition. After 13 years of teaching CIE IGCSE Biology and analysing past papers closely, we have put together the most likely topics for 2026. Use this list to focus your revision where it counts most.
How We Predict These Topics
We do not pull these predictions out of thin air.
Karishma and Khushbu have been teaching CIE IGCSE Biology for 13 years. Every year, we go through past papers from the last five to seven years. We track which topics appear every single year. We note which topics were heavily tested recently and which ones have not appeared for a while. We look at how questions are worded and what the mark schemes reward.
This tells us where CIE examiners consistently place their marks. It does not mean other topics will not appear. Every topic on the syllabus can be tested. But some topics come up year after year without fail. Those are the ones your revision must cover first and most thoroughly.
Important Note Before You Start
These predictions are based on past paper analysis and teaching experience. They are not leaked papers or inside information. CIE can test any part of the syllabus at any time. Use this guide to prioritise your revision — not to skip topics entirely.
With that said, let us get into it.
Predicted High-Priority Topics for 2026
1. Enzymes — Structure, Function, and Factors Affecting Activity
Likelihood: Very High
Enzymes appear in almost every CIE IGCSE Biology paper in some form. In 2026, expect questions on the lock and key model, how temperature and pH affect enzyme activity, and what happens when an enzyme denatures.
What to prepare:
- Explain the lock and key model using correct terms — active site, substrate, enzyme-substrate complex
- Describe what happens to enzyme activity as temperature increases past the optimum
- Explain why enzymes are specific — one enzyme, one substrate
- Know the difference between denaturation and simply slowing down
Likely question style: “Explain why increasing temperature beyond the optimum causes enzyme activity to decrease.” This is a three to four mark explain question. Students who write “the enzyme dies” lose all the marks. The correct answer uses the words denature, active site, and shape change.
2. Photosynthesis — Equations, Limiting Factors, and Leaf Structure
Likelihood: Very High
Photosynthesis is tested every year across all papers. For 2026, pay close attention to limiting factors and graph interpretation. These have appeared heavily in recent papers.
What to prepare:
- Both the word equation and the symbol equation — write them from memory without looking
- The three limiting factors: light intensity, CO₂ concentration, temperature
- How to read a limiting factors graph — what the flat section tells you
- Leaf structure and how each layer helps photosynthesis happen
- The pondweed experiment — method, variables, results, and conclusions
Likely question style: A graph showing rate of photosynthesis at different light intensities. “Explain why the rate levels off at point X.” Students must identify the new limiting factor and explain why increasing light no longer helps.
3. Respiration — Aerobic and Anaerobic
Likelihood: Very High
Respiration is one of the most misunderstood topics. Examiners know this and test it regularly. In 2026, expect a question that asks you to compare aerobic and anaerobic respiration directly.
What to prepare:
- Aerobic respiration equation: Glucose + Oxygen → Carbon dioxide + Water
- Anaerobic respiration in humans: Glucose → Lactic acid
- Anaerobic respiration in yeast: Glucose → Ethanol + Carbon dioxide
- Why aerobic releases much more energy than anaerobic
- What oxygen debt means and how lactic acid is removed after exercise
Likely question style: “A student ran a 100m sprint. Explain why their muscles used anaerobic respiration during the race and what happened to the lactic acid afterwards.” This tests both processes and the recovery mechanism in one question.
4. Transport in Humans — Heart, Blood Vessels, and Blood
Likelihood: Very High
The circulatory system is a consistently high-mark topic. For 2026, the heart structure, the differences between blood vessels, and the components of blood are all strong predictions.
What to prepare:
- The double circulation — pulmonary and systemic circuits
- Why the left ventricle has a thicker wall than the right
- Differences between arteries, veins, and capillaries — structure linked to function
- The four components of blood and what each one does
- How red blood cells are adapted for carrying oxygen — no nucleus, biconcave shape, haemoglobin
Likely question style: “Explain how the structure of a red blood cell makes it well-suited for its function.” Students must link each structural feature directly to the function — not just list features.
5. Osmosis and Water Potential
Likelihood: Very High
Osmosis questions trip up a huge number of students every year. Many students can define it but cannot apply it correctly in an experiment context. Examiners know this and keep testing it.
What to prepare:
- The definition of osmosis — movement of water molecules through a partially permeable membrane from higher to lower water potential
- What happens to a plant cell in dilute and concentrated solutions — turgor and plasmolysis
- What happens to animal cells — swelling and lysis, or crenation
- How to interpret results from a potato chip experiment in salt solutions
Likely question style: “A student placed potato chips in solutions of different salt concentrations. Describe and explain what would happen to a chip placed in a very concentrated salt solution.” This requires osmosis, water potential, and the term plasmolysis — all in one answer.
6. Genetics — Inheritance, Punnett Squares, and Sex Linkage
Likelihood: Very High
Genetics questions appear in every paper. For 2026, sex-linked inheritance is a particularly strong prediction. It has appeared in recent years and the style of question is very predictable.
What to prepare:
- All key definitions: allele, genotype, phenotype, dominant, recessive, homozygous, heterozygous
- How to set up and complete a Punnett square correctly
- Monohybrid crosses — both parents heterozygous, one parent homozygous
- Sex determination — XX female, XY male
- Sex-linked conditions — haemophilia and colour blindness as examples
- Why males are more likely to be affected by sex-linked conditions than females
Likely question style: “A woman who is a carrier for colour blindness has children with an unaffected man. Use a genetic diagram to show the possible genotypes of their children. State the probability that a son will be colour blind.”
7. Disease, Immunity, and Vaccination
Likelihood: High
This topic has grown in prominence in recent years. After global attention on vaccines and disease, CIE has tested immunity more frequently. Expect a structured question on how vaccination works.
What to prepare:
- The difference between bacterial and viral infections
- How phagocytes destroy pathogens — engulfing and digesting
- How lymphocytes produce antibodies — specific to each antigen
- How vaccination creates immunity — weakened pathogen, antibody production, memory cells
- Why a vaccinated person responds faster to the real pathogen
- What antibiotics can and cannot treat — bacteria yes, viruses no
- Why antibiotic resistance is a growing problem
Likely question style: “Explain how vaccination protects a person from a disease they have never had before.” Four marks. Students must mention the weakened pathogen, antibody production, memory cells, and the faster second response.
8. Coordination — Nervous System and Reflex Arc
Likelihood: High
The nervous system, particularly the reflex arc, is a reliable prediction for 2026. It is straightforward content but students consistently miss the relay neurone or get the direction of the impulse wrong.
What to prepare:
- The path of a reflex arc — receptor, sensory neurone, relay neurone, motor neurone, effector
- Why reflex actions are fast and do not involve conscious thought
- The difference between the central nervous system and the peripheral nervous system
- How synapses work — chemical transmission between neurones
- The structure of the eye and how it focuses light — accommodation
Likely question style: “Describe the path of a nerve impulse in a reflex arc when a person touches something hot.” Students must name each component in the correct order. Missing the relay neurone loses a mark every time.
9. Homeostasis — Blood Glucose and Kidney Function
Likelihood: High
Homeostasis is the maintenance of a constant internal environment. For 2026, blood glucose regulation and kidney function are both strong predictions. These topics have appeared across recent papers and carry high marks.
What to prepare:
- How insulin lowers blood glucose — stimulates conversion of glucose to glycogen in the liver
- How glucagon raises blood glucose — stimulates breakdown of glycogen back to glucose
- What happens in Type 1 and Type 2 diabetes
- The structure of the kidney — cortex, medulla, pelvis, ureter
- How the nephron works — filtration, reabsorption, and urine formation
- How ADH controls water reabsorption in the kidney tubules
Likely question style: “Explain how the body responds when blood glucose concentration rises above normal.” Students must mention the pancreas detecting the rise, insulin being released, and the liver converting glucose to glycogen.
10. Ecology — Food Chains, Energy Loss, and Human Impact
Likelihood: High
Ecology questions appear consistently and often carry more marks than students expect. For 2026, energy loss through food chains and the impact of humans on the environment are particularly likely.
What to prepare:
- How to construct a food chain and food web from given information
- Why energy is lost at each trophic level — respiration, heat, excretion, movement
- Why food chains rarely have more than five levels
- The carbon cycle — photosynthesis, respiration, combustion, decomposition
- The nitrogen cycle — nitrogen fixation, nitrification, denitrification
- Effects of deforestation — less CO₂ absorbed, habitat loss, soil erosion
- Effects of pollution — eutrophication in water, acid rain from sulfur dioxide
Likely question style: “A student drew a food chain with six organisms. Explain why food chains rarely have this many levels.” Students must explain energy loss through named processes, not just say “energy is used up.”
11. Cell Division — Mitosis and its Importance
Likelihood: Medium–High
Mitosis does not appear in every paper but has featured across recent years with increasing frequency. For 2026, understanding the purpose of mitosis and where it happens is more likely to be tested than memorising every stage in detail.
What to prepare:
- The purpose of mitosis — growth, repair, replacement of cells
- That mitosis produces two genetically identical daughter cells
- Where mitosis occurs — in all body cells, not in reproductive cells
- The difference between mitosis and meiosis at a basic level
- Why meiosis produces cells with half the chromosome number
Likely question style: “State two differences between mitosis and meiosis.” Or: “Explain why it is important that mitosis produces genetically identical cells.” Short answer, two to three marks.
12. Transport in Plants — Xylem, Phloem, and Transpiration
Likelihood: Medium–High
Transpiration questions often appear alongside photosynthesis. For 2026, the factors affecting transpiration rate and how to investigate transpiration using a potometer are both worth preparing.
What to prepare:
- The difference between xylem and phloem — xylem carries water upward, phloem carries sugars in both directions
- The transpiration stream — how water moves from roots to leaves
- Factors that affect transpiration rate — temperature, humidity, wind speed, light intensity
- How a potometer measures transpiration rate
- How guard cells open and close stomata
Likely question style: “A student used a potometer to measure transpiration rate in different conditions. Explain why the rate was higher on a warm windy day than on a cool still day.” Students must address both temperature and wind speed separately.
13. Human Reproduction and the Menstrual Cycle
Likelihood: Medium–High
Reproduction questions appear regularly. For 2026, the menstrual cycle and the role of hormones are a strong focus area. This is a topic many students revise too briefly.
What to prepare:
- The stages of the menstrual cycle and which hormones control each stage
- FSH stimulates egg development. Oestrogen causes the uterus lining to thicken. LH triggers ovulation. Progesterone maintains the uterus lining.
- What happens during fertilisation and where it takes place
- The role of the placenta — exchange of oxygen, glucose, CO₂, and urea between mother and foetus without blood mixing
- The role of the amniotic fluid — cushions and protects the foetus
Likely question style: “Describe the role of the placenta during pregnancy.” Students must mention what substances pass across and why the blood supplies do not mix.
14. Variation and Natural Selection
Likelihood: Medium
Evolution and natural selection appear less frequently than cell biology or genetics but have featured in recent papers. For 2026, a question explaining how antibiotic resistance develops through natural selection is a specific prediction worth preparing.
What to prepare:
- The difference between continuous and discontinuous variation with examples
- Genetic and environmental causes of variation
- Darwin’s theory of natural selection — variation, competition, survival, reproduction, inheritance
- How antibiotic resistance develops as a specific example of natural selection
- Why mutation is important as a source of genetic variation
Likely question style: “Explain how a population of bacteria can become resistant to an antibiotic over time.” Students must use the words variation, selection pressure, survival, reproduction, and inherited — in a logical order.
Topics That Could Come Up as Surprise Questions
Every few years, CIE tests a topic that students did not prepare for. These are areas worth a quick review even if they are not your main focus.
Biological molecules and food tests — knowing which reagent tests for which molecule and what a positive result looks like.
Biotechnology — uses of bacteria to make insulin, fermentation, and the basic idea of genetic engineering.
Conservation — why biodiversity matters and what methods are used to protect species and habitats.
Drugs and their effects — how alcohol, heroin, and nicotine affect the body. The difference between physical and psychological dependence.
None of these need hours of revision. One focused session on each is enough to handle a surprise question if it appears.
How to Use These Predictions in Your Revision Plan
Do not just read this list and feel ready. Feeling ready and being ready are very different things.
Here is how to use these predictions properly.
Take the first topic — enzymes. Read your notes on it for thirty minutes. Then close everything and write a full answer to this question from memory: “Explain why a high temperature destroys enzyme activity.” Check your answer. Did you use the word denature? Did you mention the active site? Did you explain that the substrate can no longer fit? If anything is missing, go back, read it again, and rewrite the answer.
Do this for every topic on this list. It takes more effort than just reading. But it is the only way to know whether you actually know the material or just feel like you do.
In the final two weeks before your exam, do timed past paper questions on these topics only. Mark your own work using the mark scheme. Look for the exact words the examiner is rewarding.
About BioKatalyst
Hi, I am Karishma. I run BioKatalyst with my partner Khushbu. We have been teaching CIE IGCSE Biology for 13 years — first in Cambridge-affiliated schools and now fully online. We have won several teaching awards over the years.
Every prediction in this guide comes from real paper analysis we do together every year. We track which topics appear, how questions are phrased, and what mark schemes reward. Then we build our teaching around that knowledge.
We teach every student ourselves. No assistants. No other tutors. Your child works directly with Karishma or Khushbu in every session. We know exactly where IGCSE students lose marks because we see it every single week in our classes. And we know how to fix it — one student, one session at a time.
Frequently Asked Questions
Are these predictions guaranteed to appear in the 2026 exam? No predictions are guaranteed. CIE can test any part of the syllabus. These are high-probability topics based on past paper patterns and 13 years of teaching experience. Use them to prioritise — not to skip other topics.
Should I revise topics not on this list? Yes. Cover your full syllabus. Use this list to decide where to spend the most time and which topics to practise with past paper questions first.
How far back should I look at past papers? Go back at least five years. Papers from 2019 to 2024 are most relevant. Look at both the May/June and October/November series. The more papers you review, the clearer the patterns become.
My child is weak in genetics and enzymes. Where should they start? Start with enzymes. The content is more contained and students can build confidence quickly. Then move to genetics — definitions first, then Punnett squares, then sex linkage. In our sessions, we always build from the simpler parts of a topic outward.
How many of these topics can you cover in one-to-one sessions? In focused one-to-one sessions, we can cover all the high-priority topics in six to eight weeks with consistent work. We move at the student’s pace — faster where they are strong, slower where they need more time.
When is the best time to book sessions before the 2026 exam? As soon as possible. Students who start three months before the exam have time to cover content properly and still complete past paper practice. Waiting until the last month means rushing through everything.
Book a Free Demo Class With Us
The 2026 exam is closer than it feels right now. The students who do well are not necessarily the smartest ones — they are the ones who prepared with focus and practised the right things in the right way.
Book a free demo class with us today. We will look at where your child stands on these predicted topics, identify the gaps, and put a plan together. One class. Real feedback. No pressure.
BioKatalyst — Online Biology Tutors | Taught directly by Karishma & Khushbu | 13 Years Experience | CIE IGCSE Specialists
