The big idea: Animal, plant and fungal cells are all eukaryotic — they all have a nucleus and membrane-bound organelles.
But they are not identical. A few key structures tell them apart:
- Plant cells have a cellulose cell wall, a large central vacuole and chloroplasts. - Fungal cells have a cell wall too, but it is made of chitin, and they have no chloroplasts. - Animal cells have no cell wall at all — just a flexible cell membrane.
All three are eukaryotic, but you tell them apart by a few structures: the animal cell has no wall (irregular shape), the plant cell has a cellulose wall, a large central vacuole and chloroplasts, and the fungal cell has a chitin wall but no chloroplasts.
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| Feature | Animal cell | Plant cell | Fungal cell |
|---|---|---|---|
| Cell wall | none | yes — made of cellulose | yes — made of chitin |
| Outer boundary if no wall | cell membrane only | — | — |
| Large permanent vacuole | no | yes (one large central one) | small vacuole(s) |
| Chloroplasts | no | yes | no |
| Usual shape | rounded / irregular | fixed, regular (often box-like) | often long thread-like hyphae |
Eukaryotic vs the cell type: Do not mix up two different comparisons.
Prokaryote vs eukaryote = do you have a nucleus? (covered in the previous lesson)
Animal vs plant vs fungal = which type of eukaryotic cell is it? — that is what this section is about.
Start by defining the structures that do the telling-apart, because the exam questions turn on these exact words.
- Cell wall
- A rigid layer OUTSIDE the cell membrane that gives the cell a fixed shape and support. Plant and fungal cells have one; animal cells do not.
- Cellulose
- The carbohydrate that makes up the PLANT cell wall.
- Chitin
- The carbohydrate that makes up the FUNGAL cell wall (the same material as in insect exoskeletons).
- Vacuole
- A fluid-filled sac. Plant cells have one LARGE permanent central vacuole that keeps the cell firm; animal cells have only small temporary ones.
- Chloroplast
- The organelle where photosynthesis happens. Found ONLY in plant cells (and some protists) — never in animal or fungal cells.
Plant cell — built for support & photosynthesis
- Cellulose cell wall → fixed, regular shape
- Large central vacuole → keeps the cell firm
- Chloroplasts → can make its own food
Fungal cell — wall, but no photosynthesis
- Chitin cell wall (not cellulose)
- Small vacuole(s); no large central one
- No chloroplasts → cannot photosynthesise
Animal cells are the odd one out: with no cell wall, only the flexible cell membrane holds them in. That is why an animal cell looks rounded or irregular, while a walled plant cell keeps a regular, fixed shape.
Atypical cells — the exceptions: Most cells have one nucleus. A few do not, and the IB calls these atypical:
- Red blood cells are anucleate — they lose their nucleus as they mature, leaving more room to carry oxygen.
- Skeletal muscle fibres and fungal hyphae are multinucleate — one long cell contains many nuclei sharing the same cytoplasm.
The shared 'atypical' feature is simply that the number of nuclei is not one.
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How this is tested: On Paper 1A you may have to identify a structure found in animal cells, or spot the atypical feature (e.g. several nuclei) shared by two odd cell types.
On Paper 2 / Paper 3 a short Explain or State question is common: explain why an animal cell looks irregular but a plant cell keeps a regular shape, or name the material of a fungal cell wall (chitin).
IB-style question — irregular animal cell vs regular plant cell
Under the microscope, cheek (animal) cells look squashed and irregular, while leaf (plant) cells keep a neat, regular shape.
Explain this difference in terms of cell structure. [2]
How to score both marks
- Identify the structural difference. The plant cell has a rigid cell wall (made of cellulose) on the outside; the animal cell has only a flexible cell membrane and no cell wall.
- Link structure to shape. The cell wall holds the plant cell in a fixed, regular shape and resists being squashed; with no wall, the animal cell's membrane lets it be pushed out of shape, so it looks irregular.
- Answer the command term (Explain). Because the plant cell has a rigid cellulose cell wall and the animal cell does not, the plant cell keeps a regular shape while the animal cell is easily deformed into an irregular one.
Final answer
The plant cell has a rigid cellulose cell wall that holds it in a fixed regular shape; the animal cell has no cell wall — only a flexible membrane — so it is easily squashed into an irregular shape.
✓ What earns the marks: Mark 1: name the structural difference (plant has a cell wall, animal does not).
Mark 2: link it to shape (rigid wall → fixed/regular shape; membrane only → deformable/irregular). Stating the difference without the consequence scores only one mark.