Animal and Plant Cells
Cells — the building blocks of life
All living things are made of cells. There are two broad types: eukaryotic cells (animal and plant cells, which have a true nucleus) and prokaryotic cells (bacteria, which don't). This note focuses on animal and plant cells and what each part does.
Animal cells
Common sub-cellular structures in an animal cell:
| Part | Function |
|---|---|
| Nucleus | Contains DNA; controls the cell's activities |
| Cytoplasm | Jelly-like fluid where most chemical reactions happen |
| Cell membrane | Controls what enters and leaves the cell |
| Mitochondria | Site of aerobic respiration – release energy |
| Ribosomes | Site of protein synthesis (making proteins) |
Plant cells
Plant cells have everything an animal cell has, plus extra structures:
| Extra part | Function |
|---|---|
| Cell wall | Made of cellulose; provides strength and support |
| Chloroplasts | Contain chlorophyll; site of photosynthesis |
| Permanent vacuole | Filled with cell sap; keeps the cell firm (turgid) |
So a quick way to remember: plant = animal + wall, chloroplasts, vacuole.
Specialised cells
Cells become specialised (differentiate) to do particular jobs. Examples:
- Sperm cell – tail for swimming, many mitochondria for energy.
- Nerve cell – long and thin to carry impulses over distances.
- Root hair cell – large surface area to absorb water and minerals.
- Red blood cell – no nucleus (more room for haemoglobin), biconcave shape.
- Muscle cell – lots of mitochondria for energy to contract.
Microscopes and magnification
We use microscopes to see cells. Light microscopes are cheaper but lower resolution; electron microscopes have much higher magnification and resolution, revealing sub-cellular detail.
Magnification formula:
magnification = size of image ÷ size of real objectRearrange as needed. Keep units the same (convert mm ↔ µm; 1 mm = 1000 µm).
Worked example
An image of a cell is 30 mm wide. The real cell is 0.06 mm wide. What is the magnification?
magnification = 30 ÷ 0.06 = ×500✓
Common mistakes
- Giving plant-only parts (cell wall, chloroplasts, vacuole) as being in animal cells.
- Saying the cell wall is made of "membrane" — it's cellulose.
- Forgetting to convert units before using the magnification formula.
Exam tips
- Learn the function of each structure in one line — a very common question.
- Remember plant cells = animal cells plus wall, chloroplasts and vacuole.
- Practise rearranging the magnification formula and converting mm ↔ µm.
Key facts to remember
- Animal cells: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes.
- Plant cells: all of the above plus cell wall (cellulose), chloroplasts, permanent vacuole.
- magnification = image size ÷ real size (keep units consistent).