# Specialised Cells
As organisms develop, their cells become specialised to carry out particular functions. This process is called differentiation, and the resulting specialised cells have structures perfectly suited to their roles.
1. Cell Differentiation
The process by which a cell becomes specialised for a particular function.
- In animals: most differentiation occurs early in development; adult stem cells replace damaged cells
- In plants: can differentiate throughout their entire life from meristem tissue
2. Specialised Animal Cells
Sperm Cell
| Adaptation | Function |
|---|---|
| Streamlined shape | Swim efficiently |
| Long tail (flagellum) | Movement |
| Many mitochondria | Energy for swimming |
| Acrosome (enzyme-filled tip) | Digest through egg membrane |
| Haploid nucleus | Contains half the chromosomes |
Nerve Cell (Neurone)
| Adaptation | Function |
|---|---|
| Long axon | Carries impulses over long distances |
| Branched dendrites | Connect to many other neurones |
| Myelin sheath | Insulation; speeds up impulse |
| Synaptic knob | Releases neurotransmitters at synapse |
Muscle Cell
| Adaptation | Function |
|---|---|
| Long and fibrous | Contract to cause movement |
| Many mitochondria | Lots of energy for contraction |
| Glycogen stores | Energy source |
Red Blood Cell
| Adaptation | Function |
|---|---|
| Biconcave disc shape | Large surface area for O₂ exchange |
| No nucleus | More space for haemoglobin |
| Contains haemoglobin | Binds and carries oxygen |
| Flexible | Squeeze through capillaries |
3. Specialised Plant Cells
Root Hair Cell
| Adaptation | Function |
|---|---|
| Long hair-like extension | Increases surface area for absorption |
| Thin cell wall | Short diffusion distance |
| Many mitochondria | Active transport of minerals |
| Large surface area:volume ratio | Efficient absorption |
Xylem Cell
| Adaptation | Function |
|---|---|
| Dead and hollow | No obstruction to water flow |
| Lignin-reinforced walls | Strength and support |
| No end walls | Continuous tube for water transport |
Phloem Cell
| Adaptation | Function |
|---|---|
| Sieve plates (porous end walls) | Allow dissolved sugars through |
| Companion cells | Provide energy (ATP) for translocation |
| Living | Active transport needed |
4. Practice Questions
- Explain how a sperm cell is adapted for its function.
- Why do red blood cells have no nucleus?
- How are root hair cells adapted for absorbing water?
- Compare xylem and phloem cells.
- What is cell differentiation?
Want to check your answers and get step-by-step solutions?
Summary
- Differentiation: cells become specialised for specific functions
- Animal cells: sperm (swimming), nerve (impulses), muscle (contraction), red blood (O₂)
- Plant cells: root hair (absorption), xylem (water transport), phloem (sugar transport)
- Each cell has structural adaptations matching its function