Cells as the building blocks of every living thing, the parts every cell shares, how cells specialise, and how tissues build organs. Concept tutorials with clickable cell and tissue diagrams.
Each lesson works two ways. Students can work through the online tutorial at their own pace (it checks their answers and saves their progress in their browser), or you can teach it to the whole class from the slides, then send students into the tutorial for the Modify and Make steps.
Every lesson guide has plain-language notes, the answers to every check, a solution for every task, and slides and a worksheet for Waypoints Prepare. These guide pages are not linked from student pages, but they are not secret either: keep printed Teacher editions for answers you do not want students to find.
All living things are made of cells, and cells share a nucleus, membrane and cytoplasm (AC9S8U01).
Cell theory: all living things are made of one or more cells; the cell is the smallest unit that carries out all life processes; cells come from other cells. That includes plants, fungi and bacteria, not just animals.
Almost every cell has three parts:
| Part | What it does |
|---|---|
| Cell membrane | A thin, flexible barrier that controls what enters and leaves |
| Cytoplasm | Jelly-like fluid where most chemical reactions happen |
| Nucleus | The control centre, holding the DNA (bacteria have no nucleus: their DNA is loose) |
Plant cells also have a cell wall (support), chloroplasts (photosynthesis) and a large vacuole (keeps the cell firm). Both have mitochondria (release energy).
Most cells are 0.01 to 0.1 mm across, below the eye's limit of about 0.1 mm; a person has about 37 trillion. Magnification = image size ÷ actual size. Cells were discovered with the microscope (Hooke 1665, Leeuwenhoek). Misconceptions: cells are about the size of sand grains; bigger animals have bigger cells.
Only plant cells have a cell wall (support), chloroplasts (photosynthesis) and a large vacuole (firmness, storage). Both have mitochondria (respiration) and ribosomes (proteins); the numbers follow the cell's job. Misconceptions: plants don't need mitochondria; all plant cells are green; animal cells have walls.
Optional ideas if you run a practical for this unit: pick one, adapt it to your equipment, or use your own.
Safety and ethics: slides and coverslips are glass: handle by the edges and report breakages. Never aim a microscope mirror at the Sun. Iodine stains skin and clothes.
Specialised cells form tissues, and tissues build organs (AC9S8U02).
Nearly every cell in your body has the same DNA, but cells specialise: they switch on different instructions and develop a shape and contents that suit one job.
| Cell | Feature | Why |
|---|---|---|
| Red blood cell | biconcave disc, no nucleus, full of haemoglobin | more room for oxygen, quick exchange, squeezes through capillaries |
| Nerve cell | long axon, many dendrites, myelin | carries signals a long way, fast |
| Muscle cell | long, many mitochondria, protein fibres | contracts, with plenty of energy |
| Root hair cell | long extension, no chloroplasts | huge surface for absorbing water underground |
Similar cells working together form a tissue (muscle tissue, epithelial lining). Several tissues working together form an organ (the heart: cardiac muscle, lining, connective tissue, nervous tissue; a leaf: epidermis, palisade and spongy mesophyll, xylem and phloem). Organs work together in organ systems.
A tissue is a group of similar specialised cells doing one job: muscle, epithelial, nervous, blood; xylem, phloem, palisade. Several tissues make an organ. Misconception: a tissue is any cells in one place, or the organ itself.
On screen: the short tutorial Organ systems covers node 4 with matching tasks and a plant and animal comparison; a physical model is still the best way in.
Optional ideas if you run a practical for this unit: pick one, adapt it to your equipment, or use your own.
Safety and ethics: nail polish is flammable: ventilate and keep away from flames. Heart rates are personal data: students may opt out, sit out for health reasons, or share only class averages; never rank individuals.