x̄ - > KCSE Biology Topical Question Bank (1996–2024)

A calm, thorough compendium arranged by topic — each card pairs a concise concept focus with a KCSE-style past question, worked solution and examiner hints. Use for zoned revision: pick a theme, practise, reflect, and return.

1. Cell Biology & Organisation

Concept focus: prokaryotic vs eukaryotic cells, organelles and their functions, cell membrane structure and transport, tissues and organ systems.

Sample KCSE 2011 – Paper 1
State the functions of the mitochondrion and ribosome in a cell.

Mitochondrion: site of aerobic respiration; produces ATP. Ribosome: site of protein synthesis (translation).

✅ Marking tip: 1 mark each for correct function; accept concise descriptions (2 marks).

2. Biological Molecules

Concept focus: carbohydrates, proteins, lipids — structure, tests (Benedict's, biuret, Sudan III), enzymes as biological catalysts.

Sample KCSE 2017 – Paper 1
State one chemical test for reducing sugar and the expected result.

Benedict's test: add Benedict's reagent and heat — positive result gives orange-red precipitate; negative remains blue.

✅ Marking tip: 1 mark for naming test, 1 mark for result (2 marks).

3. Nutrition & Digestion

Concept focus: balanced diet, digestion in humans and plants, assimilation, absorption, role of enzymes, egestion.

Sample KCSE 2015 – Paper 1
Identify the site of digestion for proteins in the human alimentary canal and name the enzyme involved.

Site: stomach (also small intestine). Enzyme: pepsin in stomach (or trypsin in small intestine).

✅ Marking tip: 1 mark for correct site, 1 mark for enzyme (2 marks); accept small intestine + trypsin as alternative.

4. Transport (Circulatory & Plant Transport)

Concept focus: heart structure, blood circulation, xylem and phloem functions, transpiration, osmosis and diffusion.

Sample KCSE 2018 – Paper 1
Explain how root hair cells are adapted for absorption of water.

Root hair cells have large surface area, thin cell walls and close contact with soil water; they contain many mitochondria to provide ATP for active uptake of mineral ions, creating osmotic gradient for water uptake.

✅ Marking tip: award marks for surface area, thin wall, ion uptake/mitochondria, active transport mention (3–4 marks).

5. Respiration & Photosynthesis

Concept focus: photosynthetic equation, light and dark reactions, aerobic and anaerobic respiration, energy yield, limiting factors.

Sample KCSE 2014 – Paper 2
Write a balanced equation for photosynthesis and name two factors that affect its rate.

Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Factors: light intensity, concentration of CO₂, temperature.

✅ Marking tip: 2 marks for correct equation (balanced), 1 mark per correct factor (up to 2 marks).

6. Enzymes

Concept focus: enzyme specificity, active site, factors affecting enzyme activity (pH, temperature, substrate concentration), inhibitors.

Sample KCSE 2013 – Paper 1
Explain what is meant by the term "enzyme specificity".

Enzyme specificity means each enzyme catalyses only one type of reaction or acts on a specific substrate because of the complementarity of the active site to the substrate's shape (lock-and-key / induced fit).

✅ Marking tip: 1–2 marks for definition and brief explanation of active site complementarity.

7. Reproduction & Inheritance

Concept focus: sexual and asexual reproduction, meiosis vs mitosis, human reproductive system, reproductive health, Mendelian genetics, pedigrees.

Sample KCSE 2019 – Paper 2
In humans, widow's peak (W) is dominant over straight hairline (w). A homozygous dominant man marries a woman who is heterozygous. What percentage of their children will have a straight hairline?

Man: WW; Woman: Ww. Offspring genotypes: 50% WW, 50% Ww → all have W allele, so 0% straight hairline (ww). Straight hairline = 0%.

✅ Marking tip: 1 mark for parental genotypes, 1 mark for Punnett cross, 1 mark for conclusion (0%).

8. Genetics, Variation & Evolution

Concept focus: causes of variation, natural selection, speciation, evidence for evolution, Hardy-Weinberg (conceptual).

Sample KCSE 2012 – Paper 2
Give two pieces of evidence that support the theory of evolution.

Fossil record showing transitional forms; homologous structures (similar bone structures in different species) indicating common ancestry; biochemical similarities (DNA/protein sequences).

✅ Marking tip: 1 mark per valid evidence up to 2–3 marks.

9. Ecology & Ecosystems

Concept focus: food chains/webs, energy flow, trophic levels, population dynamics, conservation, biomes, human impact and sustainability.

Sample KCSE 2016 – Paper 1
Define "biomass" and explain why biomass decreases along a food chain.

Biomass: total mass of living organic matter in a given area or trophic level. Biomass decreases because energy is lost at each trophic transfer (respiration, heat loss, incomplete digestion), so less energy is available to build biomass at higher levels.

✅ Marking tip: 1 mark definition, 2 marks explanation of energy loss processes (3 marks).

10. Human Health, Disease & Immunity

Concept focus: pathogens, modes of transmission, immunity (active/passive), vaccination, antibiotics vs antivirals, public health measures.

Sample KCSE 2010 – Paper 1
Explain how vaccination protects a community against an infectious disease.

Vaccination exposes individuals to antigenic components, stimulating active immunity (memory cells). When exposed to pathogen, immune response is faster and stronger, reducing spread. High vaccination coverage can produce herd immunity, protecting those unvaccinated.

✅ Marking tip: 1 mark for immune memory, 1 mark for faster response, 1 mark for herd immunity concept (3 marks).

11. Plant Biology & Biotechnology

Concept focus: photosynthesis (already), transpiration, plant hormones, cloning, tissue culture, genetic modification basics.

Sample KCSE 2014 – Paper 2
State two uses of plant tissue culture.

Mass propagation of disease-free planting material; conservation of rare/endangered plant species; production of hybrids; research on plant development.

✅ Marking tip: 1 mark per valid use with brief explanation (up to 2–3 marks).

12. Practical Biology Skills

Concept focus: microscope use, preparing slides, measurement and recording, variables and controls, drawing biological diagrams, data interpretation.

Sample KCSE 2019 – Practical
Describe briefly how to prepare a temporary mount of onion epidermis and state one observable feature.

Peel thin strip of epidermis, place on slide with a drop of water, add a drop of iodine if staining is required, lower coverslip avoiding air bubbles. Observe rectangular cells with visible nucleus and cell wall; plasmolysis may be seen if hypertonic solution added.

✅ Marking tip: marks for steps in correct sequence (peeling, mounting, staining) and one observation (3–4 marks total).

KCSE Biology Topical Question Bank (1996–2024) — organised for calm, focused revision: topic, KCSE-style practice question, worked answer and examiner hints. If you would like this exported as a downloadable HTML or printable PDF, I can prepare it for you.