Lesson focus: differentiationWhen a cell changes to become a specialised cell with a particular job. changes gene expressionWhen a gene is switched on and its instructions are used to make something, such as a protein. and cell structure so that cells perform specialised functions within an organism.
Explain specialised-cell adaptationA feature of an organism, produced by natural selection over many generations, that helps it survive and reproduce in its environment. and evaluate how differentiation creates benefits and constraints.
Build on earlier learning
Cells and organellesThe previous lesson established organelle functions. This lesson combines those structures into specialised cell designs.
You will be successful when you can…
- Define differentiation.
- Link adaptations to function.
- Compare animal and plant examples.
- Evaluate specialisation trade-offs.
Words that carry the science
- differentiation
- The process by which a cell changes to become specialised, usually through altered gene expression.
- specialised cell
- A cell with structures and activity suited to a particular function.
- gene expression
- Use of information in a gene to produce a functional RNA or protein.
- surface-area-to-volume ratio
- Surface area divided by volume; a measure affecting exchange capacity.
- stem cell
- An unspecialised cell able to self-renew and differentiate into other cell types.
- adaptation
- A feature that increases effectiveness in a particular function or environment.
Differentiation produces functional differences
01Differentiation produces functional differences
Most cells in one organism contain the same genome, but they express different sets of genes. This changes the proteins produced, which changes cell structure and activity. differentiationWhen a cell changes to become a specialised cell with a particular job. therefore creates specialised cellA cell with a special shape or features that help it do one job, like a red blood cell carrying oxygen. without requiring a different full set of DNA.
Early animal cells often lose the ability to become many cell types as development continues. Plants retain dividing meristem cells in growing regions throughout life.
02Adaptations must be linked to a task
Red blood cells have a biconcave shape, haemoglobin and no nucleus when mature, increasing space and effective surface area for oxygen transport. Neurones have long axons and branched connections for rapid communication. Sperm cells combine a flagellum, many mitochondria and an acrosome for fertilisation.
Root hair cells have a long projection for absorption, a thin exchange surface and many mitochondria for active uptake of mineral ions. Palisade cells contain many chloroplasts and are positioned for light absorption.
03Specialisation creates dependence
A mature red blood cell cannot divide or replace its proteins efficiently, so it has a limited lifespan. A long neurone communicates over distance but depends on support cells and a stable supply of oxygen and glucose.
Stem-cell therapies may replace damaged cells, but potential benefit must be balanced against immune rejection, uncontrolled division, incomplete differentiationWhen a cell changes to become a specialised cell with a particular job. and ethical questions about cell sources.
Build a structure–function explanation
Explain why a root hair cell contains many mitochondria.
- Identify the function: uptake of mineral ions from soil.
- Recognise that ions may move against a concentration gradient.
- Name the process: active transport.
- Link mitochondria to aerobic respiration and ATP supply.
How to make the reasoning visible: Many mitochondria support ATP production for active-transport proteins; they do not pull ions in directly.
Match adaptation to evidence
Complete the causal link from structure through mechanism to function.
| Cell | Adaptation | Mechanism | Function |
|---|---|---|---|
| red blood cell | biconcave and no nucleus | large exchange surface and space for haemoglobin | oxygen transport |
| neurone | long axon and branched ends | conducts and connects over distance | rapid communication |
| root hair cell | long projection; many mitochondria | large surface and ATP-supported transport | water and mineral uptake |
| sperm cell | flagellum; mitochondria; acrosome | movement and enzyme release | reach and penetrate egg |
Why is “long” alone not a complete explanation for a neurone?
Why does removing a red blood cell nucleus create a trade-off?
Check your understanding
Answer from memory, then check against the suggested answer.
What is differentiation?
Why do root hair cells contain many mitochondria?
What does haemoglobin do?
A patient has damaged insulin-producing cells. Why is adding generic stem cells not immediately a cure?
How can cells with the same genome have different shapes?
Exam Question Practice
Exam Question Practice
Mark points shown after marking
A mature red blood cell is specialised to transport oxygen.
Explain how the structure of a red blood cell is adapted for oxygen transport.
(5)State one consequence of the cell having no nucleus.
(1)Total for this question: 6 marks
Command word: For explainA command word: say how or why something happens, giving reasons with words like "because" or "so"., write linked structure → mechanism → function statements, then state the trade-off.