GCSE Biology · Edexcel 1BI0 · Topic 1A
Cell structure and microscopy
Key points
- Animal cells have a nucleus, cell membrane, cytoplasm, mitochondria and ribosomes. Plant cells also have a cellulose cell wall, chloroplasts and a large permanent vacuole.
- Bacterial cells are prokaryotic: a single loop of chromosomal DNA, small rings of DNA called plasmids, a cell wall and sometimes a flagellum. They are much smaller than eukaryotic cells.
- Specialised cells: sperm (acrosome with enzymes, many mitochondria, tail), egg (food store in cytoplasm, membrane that changes after fertilisation), ciliated epithelial cells (cilia that sweep mucus).
- . Convert units first: 1 mm = 1000 µm, 1 µm = 1000 nm.
- Electron microscopes give higher magnification and resolution (the ability to tell two close points apart), so they show sub-cellular structures like ribosomes in detail.
- Use standard form for tiny sizes, e.g. 0.000002 m = m.
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Every living thing is built from cells, and each part of a cell has a specific job. This sub-topic covers the structures inside animal, plant and bacterial cells, how some cells are specialised, and how to calculate sizes and magnifications…
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