What you need to know
- Define cell specialisation.
- Recognise common specialised animal and plant cells.
- Explain how particular structural features support a cell's function.
- Connect specialised cells to tissues, organs and systems.
What is cell specialisation?
Cells in a multicellular organism begin with the same genetic information, but they develop different structures and activate different genes. This process is differentiation. The resulting specialised cells are suited to particular jobs.
A feature that helps a cell or organism perform its function or survive in its environment.
A complete structure–function explanation follows the chain: feature → immediate effect → advantage for the function.
Specialised animal cells
| Cell | Function | Adaptations |
|---|---|---|
| Sperm cell | Reaches and fertilises an egg. | A flagellum propels it; many mitochondria transfer energy for movement; an acrosome contains enzymes to digest the egg's outer layers; the nucleus is haploid. |
| Egg cell | Fuses with a sperm and supports early development. | A haploid nucleus combines with the sperm nucleus; nutrient-rich cytoplasm supports the early embryo; the membrane changes after fertilisation to block additional sperm. |
| Nerve cell | Transmits electrical impulses. | A long axon carries impulses over distance; branched endings connect with other cells; insulation speeds transmission. |
| Muscle cell | Contracts to produce movement. | Contains contractile protein fibres and many mitochondria to meet the energy demand. |
| Ciliated epithelial cell | Moves material across a surface. | Hair-like cilia beat to move mucus in airways or move an egg along an oviduct. |
| Red blood cell | Transports oxygen. | Biconcave shape gives a large surface area; packed with haemoglobin; no nucleus leaves more space for haemoglobin; flexible to pass through capillaries. |
Specialised plant cells
| Cell | Function | Adaptations |
|---|---|---|
| Root hair cell | Absorbs water and mineral ions. | A long projection creates a large surface area; thin wall gives a short diffusion distance; many mitochondria provide energy for active transport of mineral ions. |
| Palisade cell | Carries out photosynthesis. | Contains many chloroplasts and is positioned near the upper surface of the leaf to receive light. |
| Xylem vessel | Transports water and mineral ions and supports the plant. | Dead cells join into hollow tubes; no end walls obstruct flow; lignin strengthens and waterproofs the walls. |
| Phloem cell | Transports dissolved sugars. | Sieve-tube elements form columns with perforated end plates; companion cells contain mitochondria that support transport. |
Misconception AlertA root hair is a tiny multicellular root.Select to reveal the correctionSelect to hide the correction
A root hair cell is one specialised epidermal cell with a long projection that increases its surface area.
How to explain an adaptation
Weak answer
“A sperm cell has many mitochondria for energy.”
Strong answer
“A sperm cell contains many mitochondria, which carry out aerobic respiration and transfer energy for movement of the flagellum, helping the sperm reach the egg.”
Avoid saying that cells have features “because they need them”. State the mechanism and the benefit.
If the question gives an unfamiliar cell, use the same reasoning. Look for a large surface area, short diffusion distance, many mitochondria, an elongated shape or a high number of a particular organelle.
Quick retrieval check
1. Why does a sperm cell have many mitochondria?
2. How is a root hair cell adapted for absorption?
3. Why does a red blood cell have no nucleus?
4. How does lignin help a xylem vessel?
Exam connection
An intestinal epithelial cell has microvilli on its surface and many mitochondria. Explain how these features help absorption.
Show the mark points
- Microvilli increase the surface area.
- This increases the rate of absorption.
- Mitochondria carry out aerobic respiration.
- They transfer energy for active transport of substances such as glucose.