Cell Organisation
Year 7 ๐ฌ Cell Biology & Biochemistry From cells to tissues, organs, and organ systems.
๐งซ The Organisation Hierarchy
Living organisms are organised from the smallest unit (cell) up to the whole organism.
Hierarchy (smallest โ largest)
Cell โ Tissue โ Organ โ Organ System โ Organism- Cell โ the basic unit of life (e.g. muscle cell, nerve cell)
- Tissue โ a group of similar cells carrying out the same function (e.g. muscle tissue)
- Organ โ different tissues working together (e.g. heart = muscle + epithelial + nervous tissue)
- Organ system โ organs with a shared purpose (e.g. digestive system)
- Organism โ a complete living thing
๐ฌ Specialised Cells
Cells differentiate (become specialised) during development. Structure relates to function.
| Cell | Key adaptations | Function |
|---|---|---|
| Red blood cell | Biconcave disc, no nucleus, packed with haemoglobin | Transport Oโ |
| Sperm cell | Tail (flagellum), many mitochondria, acrosome on head | Fertilise egg |
| Ciliated epithelial | Tiny cilia on surface, many mitochondria | Move mucus in airways |
| Root hair cell | Long hair-like extension, large surface area, no chloroplasts | Absorb water and minerals |
| Palisade mesophyll | Many chloroplasts, near leaf surface | Photosynthesis |
| Guard cell | Kidney-shaped, large vacuole, chloroplasts | Open/close stomata |
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