Explain why plant cells have both a cell membrane and a cell wall, whilst animal cells only have a cell membrane.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A student observing plant and animal cells under a light microscope notices that plant cells appear to have an extra outer layer that animal cells do not possess.
Model answer (4 marks)
Plant cells have a cell wall in addition to the cell membrane. The cell wall, made of cellulose fibres, gives the cell strength and support, helping the cell maintain its shape and turgidity. The cell membrane, present in both plant and animal cells, is a selectively permeable barrier that controls the movement of substances into and out of the cell. Animal cells do not require a cell wall because they do not need the same structural support; their cells are smaller and rely on the membrane alone for shape and protection.
Examiner tips
- Use the exact terms ‘cell wall’, ‘cell membrane’, ‘cellulose fibres’, ‘selectively permeable barrier’.
- Explain the function of each structure and why the wall is unnecessary for animal cells. 4 marks are awarded for covering all four points.
- Keep the answer short and to the point – no extra sentences.
- Mention turgidity or structural support for plant cells.
Common mistakes
- Writing that the cell membrane is only in plant cells, or that the cell wall is only in animal cells.
- Using vague terms like ‘support’ without specifying cellulose fibres or turgidity.
- Adding unnecessary details such as chloroplasts or mitochondria.
Mark scheme (4 marks)
- The cell wall provides strength and support to the plant cell
- The cell wall is made of cellulose fibres
- The cell membrane is a selectively permeable barrier that controls the movement of substances into and out of the cell
- Animal cells do not need a cell wall because they do not need the same structural support / plant cells need extra support due to their larger size or to maintain turgidity
Key terms in this question
Related
- Revision notes: Cell structures →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Cell structures questions
- A palisade mesophyll cell and a human cheek cell are both eukaryotic cells. Expl…
- A bacterial cell is a prokaryotic cell. Explain why bacterial cells do not have …
- A yeast cell is a eukaryotic cell. Explain why a yeast cell contains mitochondri…
- A student observing a cell under a light microscope notices several distinct org…