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🎯 How to revise with this site
Read Living Things and Cells — learn the organelles and the kingdoms.
Study Transport — diffusion vs osmosis vs active transport is guaranteed to come up.
Do the Quiz Zone — MCQ quiz, matching game, and label-the-cell.
Re-take quizzes until you score 90%+. Your best scores are saved.
Use the Glossary to look anything up fast.
🏆 Your best scores
Quiz
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MCQ Quiz
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Matching game
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Label the cell
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✨ Lesson 1 — Characteristics of Living Organisms
🎓 Exam need-to-know: you must be able to describe each characteristic — not just name it. 2-mark questions usually want a short explanation.
MRS C GREN — the 8 characteristics of life
Letter
Characteristic
What it means
M
Movement
Moving part of the organism, or moving things inside it
R
Respiration
Releasing energy from food (glucose) — usually by aerobic respiration in mitochondria
S
Sensitivity
Detecting and responding to changes in the surroundings (stimuli)
C
Control
Controlling internal conditions (homeostasis) — e.g. body temperature, water levels
G
Growth
Getting bigger / increasing in size
R
Reproduction
Making more of the same kind of organism
E
Excretion
Removing waste products of metabolism (e.g. CO₂, urea)
N
Nutrition
Taking in food/raw materials for energy and growth
⚠️ Common trap: excretion (getting rid of waste made by the body) is NOT the same as egestion (getting rid of undigested food). And "digestion" is NOT a characteristic of life on its own!
Quick True/False — check yourself
Statement
True/False?
All living organisms have eyes
False
All living organisms breathe (gas exchange)
True — they exchange gases for respiration
All living organisms need nutrition
True
All living organisms can reproduce
True
All living organisms do digestion
False — simple organisms absorb food directly
🔬 Jellyfish question (from your booklet!)
The booklet uses jellyfish as a classic exam question. Evidence jellyfish are living:
They feed on small fish caught in tentacles (nutrition)
They take in oxygen and respire
They respond — nerve net coordinates responses
They reproduce — release sperm/eggs, and some clone themselves
They move — rhythmic pulsations of the umbrella
💡 Technique: these questions want evidence FROM the passage + linking it to the characteristic name. Quote → name → explain.
The 5 Kingdoms + viruses — classification table
Kingdom
Multicellular?
Nucleus?
Key features
Examples
Animal
Yes
Yes (eukaryote)
No cell wall, no chloroplasts, nervous co-ordination, store glycogen
Human, housefly, mosquito
Plant
Yes
Yes (eukaryote)
Chloroplasts + photosynthesis, cellulose cell wall, store starch/sucrose
Maize (cereal), peas, beans
Fungi
Mostly (yeast is single-celled)
Yes (eukaryote)
Chitin cell wall, hyphae form a mycelium, saprotrophic nutrition (enzymes onto food, absorb), store glycogen
Mucor, yeast
Protoctist
No (single-celled)
Yes (eukaryote)
Microscopic; some animal-like (Amoeba), some plant-like (Chlorella)
Amoeba, Chlorella, Plasmodium (malaria)
Bacteria
No (single-celled)
No (prokaryote)
Cell wall, membrane, cytoplasm, plasmids, circular chromosome; some photosynthesise
Lactobacillus (yoghurt), Pneumococcus (pneumonia)
Viruses (not a kingdom)
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No — no cells at all!
Protein coat + DNA or RNA, only reproduce inside living cells, parasitic
TMV, influenza, HIV
🎓 Key phrase: "Viruses are not living organisms — they are small particles made of a protein coat around one type of nucleic acid (DNA or RNA) and can only reproduce inside living cells."
🧫 Lesson 2 — Animal & Plant Cells
🎓 The diagrams below are drawn to match the ones in your booklet. Learn to draw + label a plant cell from memory — it's a guaranteed 3 marks in the exam.
⚖️ Plant vs animal cell — the differences (classic 3-mark Q)
Plant
Animal
Cell wall
✅ Cellulose cell wall (rigid)
❌ No cell wall
Chloroplasts
✅ Yes (photosynthesis)
❌ No chloroplasts
Vacuole
✅ Large permanent vacuole with cell sap
❌ No large vacuole (small/absent)
Carbohydrate storage
Starch / sucrose
Glycogen
Shape
Regular / rigid
Irregular, flexible
🎓 The booklet also tests Chlamydomonas — a single-celled protoctist with chloroplasts, flagella and an eyespot. It's not a plant because it's single-celled and can swim using flagella. It gets energy by photosynthesis and its flagella let it move.
Bacterium: cell wall/membrane, cytoplasm, circular DNA (no nucleus!), plasmids, ribosomes, sometimes a flagellum. Prokaryote = no nucleus.
Virus (NOT living)
Virus: protein coat around one type of nucleic acid (DNA or RNA). No cells, no cytoplasm, no organelles — only reproduces inside a host cell. Not living!
🔭 The light microscope
Light microscope: eyepiece → tube → objective lenses → stage (holds slide with clips) → lamp. Coarse focus (find specimen, low power only) then fine focus (sharpen; never coarse at high power).
🎓 Magnification: Magnification = image size ÷ actual size. Total = eyepiece × objective (e.g. 10 × 40 = 400×).
⚠️ SAFETY: Never touch the eyepiece/objective glass (use lens tissue). At high power, use only the fine focus knob — using the coarse knob can crack the slide or damage the lens!
How to use a microscope — correct order
Switch on the microscope (turn on the lamp).
Turn the nosepiece so the low-power objective clicks into place above the stage.
Place your slide on the stage and secure it with the stage clips.
Use the rough/coarse focus knob to move the stage to its lowest position.
Look through the eyepiece and locate the specimen using the coarse knob (adjust slide position with the stage).
Once in focus, increase magnification by turning the nosepiece to a higher-power objective.
Sharpen with the fine focus knob — do NOT use the coarse knob (damages lens / cracks slide).
🌊 Lessons 3–6 — Diffusion, Osmosis & Active Transport
🎓 This is the highest-mark topic in Unit 1. You MUST be able to compare all three processes in a table (2.15) and explain the factors that affect rate (2.16).
💨 Lesson 3 — Diffusion
Diffusion = net movement of particles from high → low concentration (down the gradient), until evenly spread.
📌 Definition (memorise): Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration (down the concentration gradient). It is a passive process — no energy needed.
What can diffuse in/out of cells?
Into: oxygen, glucose, amino acids, mineral ions, water
Out of: carbon dioxide (waste), urea
🧊 Surface area : volume ratio — why size matters
SA:Vol = surface area ÷ volume. Small cube: 6 ÷ 1 = 6. Bigger cube: (6×4²)÷(4³) = 96÷64 = 1.5.
The agar cube practical from your booklet: cubes of agar soaked in acid lose their pink colour as acid diffuses in. The small cubes clear fastest because they have a higher SA:Vol. As cube size doubles, surface area quadruples (×2²) but volume goes up ×8 (×2³) — so the ratio shrinks.
⚠️ Exam link (2.51): "Explain why simple unicellular organisms can rely on diffusion but humans can't." → Single cells have a large SA:Vol, so diffusion across the membrane is fast enough. Large organisms have a small SA:Vol → diffusion is too slow → they need transport systems (blood, lungs, heart).
💧 Lesson 4 — Osmosis
Osmosis: water moves from dilute → concentrated solution through a partially permeable membrane. Orange = solute (too big to pass).
📌 Definition (memorise): Osmosis is the net movement of water molecules from a dilute solution to a more concentrated solution through a partially permeable membrane. It's diffusion of WATER, and it's passive (no energy).
⚠️ Direction of water: water always moves to the side with more solute / less water — i.e. "from where there's lots of water to where there's less".
🔴 What happens to an ANIMAL cell?
Animal cells have NO cell wall — too much water in → they swell and can burst (lyse). Too little → they shrink.
🌱 What happens to a PLANT cell?
Plant cells are protected by the cell wall. Turgid = full of water, firm. Plasmolysed = water lost, membrane pulls away from wall.
Turgid: dilute solution → water enters, vacuole swells, presses against cell wall → turgor pressure keeps plant firm.
Flaccid: isotonic → water in = water out → no turgor pressure.
Plasmolysis: concentrated solution → water leaves, membrane + cytoplasm pull away from cell wall → plant wilts.
🥔 Potato practical (Lesson 5) — the classic osmosis investigation
Potato cubes in different concentrations of sugar solution (0 to 1.0 mol dm⁻³).
Concentration
What happens
Why
0 mol dm⁻³ (pure water)
Mass increases
Water enters cells by osmosis (cell sap more concentrated than outside)
Low sugar
Mass increases a little
Water still enters — outside still more dilute than cell sap
≈ isotonic
Mass stays the same
No net movement — same water concentration (this is the concentration of the cell sap!)
High sugar
Mass decreases
Water leaves the cells by osmosis
🎓 Variable names (learn these!): Independent = sugar concentration. Dependent = change in mass. Control variables = same potato size/mass, same temperature, same time, same solution volume. Use % change in mass (not raw change) so cubes with different start masses can be compared fairly.
📈 Reading the graph: as concentration ↑, % change in mass ↓. Where the line crosses 0% change = the isotonic concentration = concentration of the potato cell sap.
⚡ Lesson 6 — Active Transport
Active transport: carrier proteins use energy from ATP to pump ions/molecules against the concentration gradient (low → high).
📌 Definition (memorise): Active transport is the movement of substances from a more dilute solution to a more concentrated solution (against the concentration gradient). It requires energy from respiration (ATP) and uses carrier proteins in the membrane.
⚡ Needs energy (ATP) from aerobic respiration in mitochondria
🔁 Goes AGAINST the gradient (low → high concentration)
🧬 Uses carrier proteins — specific to each substance
🥔 Example: root hair cells absorbing mineral ions (e.g. nitrate) from very dilute soil water
🍞 Example: small intestine epithelial cells absorbing glucose and amino acids
🎓 Why lots of mitochondria? Cells doing active transport need lots of energy → they contain many mitochondria. That's why the exam loves epithelial cells + root hair cells.
⚠️ Cyanide experiment (know this!): cyanide stops respiration → no ATP → active transport stops. In the booklet's table, glucose and galactose absorption dropped with cyanide (they need active transport), but xylose and arabinose stayed the same (diffusion only, no energy needed).
⚖️ The comparison table — diffusion vs osmosis vs active transport
💨 Diffusion
💧 Osmosis
⚡ Active transport
What moves
Any particles (gas/liquid)
Water only
Ions / molecules (e.g. glucose, nitrates)
Direction
High → low conc (down)
High water → low water (through membrane)
Low → high conc (against)
Energy needed?
❌ No (passive)
❌ No (passive)
✅ Yes — ATP from respiration
Membrane needed?
No (can be in air/liquid)
Yes — partially permeable
Yes — carrier proteins
🎓 Exam phrase: diffusion and osmosis are passive (require no energy); active transport requires energy and goes against the gradient.
🦠 Lesson 7 — Pathogens & Disease
🎓 A pathogen is a microorganism that causes infectious disease. Pathogens can be fungi, bacteria, protoctists or viruses (1.4).
What each type of pathogen does
Type
What it is
How it harms us
Example disease
Bacteria
Single-celled prokaryotes
Reproduce fast in the body; release toxins that damage tissue
Cholera, pneumonia, food poisoning (Salmonella)
Fungi
Eukaryotes with hyphae (or single-celled like yeast)
Grow on/in skin or plants; damage tissue
Ringworm
Protoctists
Single-celled eukaryotes
Enter blood / cells; damage tissues
Malaria (Plasmodium)
Viruses
Protein coat + DNA/RNA, no cells
Invade cells, reproduce inside them, destroy them
Flu, HIV/AIDS, Tobacco Mosaic Virus
Diseases table — cause, spread, symptoms
Disease
Pathogen type
How it's spread
Symptoms
Flu (influenza)
Virus
Airborne droplets (coughing/sneezing)
Fever, aches, fatigue
Pneumonia
Bacterium (Pneumococcus)
Airborne droplets
Inflamed lungs, difficulty breathing
Ringworm
Fungus
Direct skin contact / contaminated surfaces
Itchy, circular skin rash
Cholera
Bacterium
Contaminated water / food
Severe diarrhoea, dehydration
Tobacco Mosaic Virus (TMV)
Virus
Contact between plants / insects
Discoloured (mosaic) leaves — chloroplasts destroyed → less photosynthesis
Malaria
Protoctist (Plasmodium)
Mosquito bites (vector = mosquito)
Fever, chills, weakness
HIV / AIDS
Virus
Body fluids (blood, sexual contact)
Destroys immune cells → AIDS
💡 Key facts to remember
TMV prevents chloroplast formation → leaves lose colour → plant can't photosynthesise as well → less growth.
Malaria's vector is the mosquito — the pathogen Plasmodium is a protoctist (single-celled eukaryote!).
Viruses are not cells — they hijack host cells to reproduce.
The disease is not the pathogen — the pathogen causes the disease.
📝 Quiz Zone
Three ways to test yourself. Best scores are saved on this computer.
Choose how many questions:
Match each organelle/structure to its function. Click one from each column. Found 0/10
Click a numbered dot on the plant cell, then pick the matching structure.
📋 Exam technique — command words
Word
What you must do
Describe
Say what something is or what happens — no reason needed
Explain
Give a reason / mechanism ("because…")
Suggest
Use your knowledge to give a sensible answer (marks for any valid idea)
State / Name
Short answer, one word or phrase
Compare
Mention BOTH things + a similarity OR difference
🎓 Definition questions = free marks. Learn the three definitions cold: diffusion, osmosis, active transport. Always include "down/against the concentration gradient" and "partially permeable membrane" / "energy from respiration" — those phrases ARE the marks.