Topics · Primary Science · Systems: Cells
Cells: what living things are built from
Every living thing is made of cells. Plant cells and animal cells share most parts and differ in three, and those three differences are what nearly every question is about.
- 188 exam papers analysed
- appears in 63% of P6 Science papers
- ~3 min read
01 The building blocks
A cell is the smallest unit of a living thing. Some living things are a single cell; humans are made of a great many.
Cells are too small to see without a microscope, which is why this topic always involves one.
Cells of the same kind group into tissues, tissues into organs, organs into systems, and systems into a whole organism — the ladder P6 questions ask you to place something on.
02 The three differences
Plant and animal cells both have a cell membrane, cytoplasm and a nucleus. Only three parts differ, and they are worth knowing exactly.
| Part | Plant cell | Animal cell |
|---|---|---|
| Cell wall | ✓ | ✗ |
| Chloroplasts | ✓ | ✗ |
| Large vacuole | ✓ | small or none |
| Cell membrane | ✓ | ✓ |
| Cytoplasm | ✓ | ✓ |
| Nucleus | ✓ | ✓ |
- Cell wall — plant only. Rigid, outside the membrane, giving the cell its fixed shape.
- Chloroplasts — plant only, and only in the green parts. They hold chlorophyll and make food.
- Large vacuole — plant cells have one big one storing water; animal cells have small ones or none.
03 What each part does
Questions ask for the job, so learn the parts by what they do.
- Cell membrane — controls what enters and leaves the cell. Both kinds have one.
- Cytoplasm — the jelly where the cell's activities happen.
- Nucleus — controls the cell and holds the information it needs.
- Cell wall — supports the plant cell and keeps its shape.
- Chloroplast — makes food using sunlight.
- Vacuole — stores water and keeps the plant cell firm. A wilting plant is one whose vacuoles have lost water.
04 Identifying a cell in a picture
The standard question shows an unnamed cell and asks whether it is plant or animal, and how you know.
A rigid, regular, boxy outline suggests a cell wall, so a plant cell. A rounded, irregular outline suggests an animal cell.
Green dots are chloroplasts, so a plant cell — but a root cell is a plant cell with no chloroplasts at all, because it gets no light. That is the trap, and the answer is the cell wall, not the colour.
Name a part you can actually see in your reason. “It has a cell wall” scores; “it looks like a plant cell” does not.
05 How to say them
These are words most children have never said out loud, and a word you cannot say is a word you avoid using. Capitals mark the syllable you lean on. Tap the speaker to hear it.
- cellmore than onecells
The smallest unit a living thing is made of.
- cell membranesayMEM-brayn
The thin layer controlling what goes in and out. Both plant and animal cells have one.
- cell wall
The rigid layer outside a plant cell's membrane, giving it shape. Animal cells have none.
- cytoplasmsaySY-tuh-plaz-uhm
The jelly filling the cell, where its activities happen.
- nucleussayNYOO-klee-uhsmore than onenuclei
The part that controls the cell.
- chloroplastsayKLOR-uh-plastmore than onechloroplasts
The green part of a plant cell that makes food using sunlight.
- vacuolesayVAK-yoo-ohlmore than onevacuoles
A space storing water. Large in plant cells, small or absent in animal ones.
06 What each level is tested on
The same topic, asked differently as it goes up. The percentage is the share of papers at that level in which it appears.
- P5
What cells are, the parts of plant and animal cells, and the differences between them.
Practise P5 Systems: Cells — 10 questions →55% of P5 papers
- P6
The jobs of each part, identifying a cell from a picture, and cells inside systems questions.
Practise P6 Systems: Cells — 9 questions →63% of P6 papers
07 Mistakes worth knowing about
Each of these is wrong. Decide why before you open it.
“Plant cells have a cell wall instead of a membrane.”
They have both. The wall is outside the membrane, and every cell has a membrane.
“All plant cells have chloroplasts.”
Only the parts that get light. Root cells are plant cells with none.
“It is green, so it is a plant cell.”
Use the cell wall — it is present in every plant cell, including ones with no chloroplasts at all.
“Animal cells have no vacuoles.”
They can have small ones. The difference is that a plant cell has one large one.
“A cell is the same as an organ.”
Cells make tissues, tissues make organs. An organ is made of a great many cells.
Now try it
19 questions across 2 levels, marked as you go with the working shown.