Cells โ The Building Blocks of Life
Year 7 ๐ฌ Cell Biology & Biochemistry Explore plant and animal cells, organelles, and how to use a microscope.
๐ฌ Animal vs Plant Cells
Cells are the basic structural and functional units of all living organisms. Most cells are too small to see without a microscope.
| Feature | Animal cell | Plant cell |
|---|---|---|
| Cell membrane | โ | โ |
| Nucleus | โ | โ |
| Cytoplasm | โ | โ |
| Mitochondria | โ | โ |
| Ribosomes | โ | โ |
| Cell wall (cellulose) | โ | โ |
| Chloroplasts | โ | โ (green parts only) |
| Large permanent vacuole | โ | โ |
Memory trick: Plant cells have three extras โ Wall, Chloroplasts, Vacuole (WCV).
๐ฌ Organelle Functions
Each organelle has a specific role. Questions often ask you to match structure to function.
- Nucleus โ controls cell activity; contains DNA (genetic instructions)
- Mitochondria โ site of aerobic respiration; releases energy as ATP
- Ribosomes โ site of protein synthesis
- Cell membrane โ controls substances entering and leaving (selectively permeable)
- Cell wall (plants) โ cellulose; provides structural support and rigidity
- Chloroplasts (plants) โ contain chlorophyll; carry out photosynthesis
- Vacuole (plants) โ contains cell sap; keeps cell turgid
๐ Microscopy and Magnification
Cells are measured in micrometres (ฮผm). 1 mm = 1000 ฮผm.
Magnification formula
$$M = \frac{I}{A}$$ M = magnification, I = image size, A = actual size- Light microscopes: max magnification ~ร1500, limited resolution
- Electron microscopes: much higher magnification and resolution โ can see organelles like ribosomes and mitochondrial cristae
- Always include units (ฮผm, mm) in microscopy calculations
Convert units before calculating: 1 mm = 1000 ฮผm. If the image is 30 mm and magnification is ร500, actual size = 30 mm รท 500 = 0.06 mm = 60 ฮผm.
Ready to test yourself? Click the Quiz tab above!
Interactive Demo โ Cells โ The Building Blocks of Life
Select a cell type and click Draw Cell.
Magnification Calculator
M = I / A โ magnification = image size รท actual size