Cells and organisation · GCSE Biology
Specialised cells
Link structure to function in GCSE Biology specialised cells: sperm, egg, nerve, muscle, root hair, palisade, xylem and phloem, with the adaptation sentences that score.
Same genome, different job. Name the feature, then the advantage: mitochondria for energy, surface area for exchange, lignin for strength, acrosome for enzymes.
The important bits
What you need to know
- 1
A specialised cell is differentiated: it has a structure matched to one function. Differentiation happens as cells mature; most animal cells then cannot change type.
- 2
Sperm cell: streamlined head, flagellum for swimming, many mitochondria to transfer energy for movement, acrosome containing enzymes to digest the egg’s zona pellucida.
- 3
Egg cell: large cytoplasm with nutrient stores for the early embryo, haploid nucleus, and a membrane that changes after fertilisation so only one sperm can enter.
- 4
Nerve cell (neurone): long axon to carry electrical impulses over distance, myelin sheath in many neurones to speed conduction, synaptic endings that release neurotransmitter.
- 5
Muscle cells: protein fibres that slide to contract, many mitochondria for aerobic respiration during contraction.
- 6
Root hair cell: long hair-like extension increases surface area for water (osmosis) and mineral ions (active transport); many mitochondria; no chloroplasts (underground).
- 7
Palisade mesophyll cell: column-shaped, packed with chloroplasts, located at the top of the leaf to absorb light for photosynthesis.
- 8
Xylem: dead cells, hollow lumen, lignin rings or spirals for strength and to withstand tension; transports water and mineral ions from roots to leaves. Phloem: living sieve tubes with companion cells, transports dissolved sugars (translocation).
Quotations worth analysing
Short evidence. Real method.
“Name the structural feature and explain how it helps the cell carry out its function.”
“It is adapted” scores zero. “Large surface area so more water is absorbed by osmosis” scores.
“Root hair cells have a large surface area and many mitochondria for active transport of mineral ions.”
Surface area covers osmosis of water; mitochondria cover energy for ions against the gradient. Write both if the question allows.
“Sperm cells contain an acrosome of enzymes and mitochondria for swimming.”
Acrosome is the enzyme packet; mitochondria are not in the acrosome. Keep the two adaptations separate.
Go deeper
How do I turn a specialised-cell question into four marks?
Use a two-part sentence per mark: feature plus advantage. Sperm: flagellum — swims to the egg; mitochondria — transfer energy for movement; acrosome — enzymes digest the egg membrane; haploid nucleus — so fertilisation restores 46 chromosomes. Root hair: long projection — large surface area for osmosis of water; mitochondria — energy for active transport of nitrate ions; thin wall — short diffusion path. Palisade: many chloroplasts — more photosynthesis; tightly packed columns — catch light near the upper epidermis. Nerve: long axon — impulse travels the length of the body; synapses — chemical transfer to the next cell. Stop after the named cell in the question. Writing every cell you know wastes time and still misses the structure–function link if you only list names.
Go deeper
Why do root hair cells have no chloroplasts if they are plant cells?
They are underground, so light does not reach them. Chloroplasts would be wasted volume. The cell invests in surface area and mitochondria instead, because its job is uptake, not photosynthesis. Water enters by osmosis from dilute soil solution into more concentrated cell sap. Mineral ions such as nitrate are often more concentrated inside the cell than in the soil, so they cannot arrive by diffusion alone: carrier proteins in the membrane use energy from respiration (active transport). That is why cyanide, which stops respiration, also stops ion uptake in classic experiments. In the exam, “no chloroplasts because it is a root” is incomplete; add “no light so it does not photosynthesise”.
Go deeper
What is the difference between xylem and phloem in one paragraph?
Xylem carries water and dissolved mineral ions from roots to leaves in one direction, pulled by transpiration. The cells are dead, end walls broken down, lignin in the walls so the tube does not collapse under tension and so the stem is supported. Phloem carries dissolved sugars (from photosynthesis, as sucrose) from leaves to sinks such as roots, fruits and growing tips, in either direction (translocation). Phloem cells are living sieve-tube elements with pores in the end walls and companion cells packed with mitochondria to load sugar by active transport. A common error is “xylem carries food” or “phloem carries water”. Match the contents: xylem = water + ions; phloem = sugars. Both are specialised plant cells forming tissues.
See the idea in action
Explain how a sperm cell is adapted (4 marks). Streamlined head reduces resistance as it swims. Flagellum beats to propel the cell to the egg. Many mitochondria transfer energy from aerobic respiration for movement. Acrosome contains enzymes that digest the egg membrane so the haploid nucleus can enter. Each point is feature + job. “It is adapted to swim” alone would score zero.
Exam technique
Turn knowledge into marks
If the question names one cell, give two or three adaptations in feature–advantage pairs. For “compare sperm and egg”, contrast numbers (many small sperm versus one large egg), movement (flagellum versus stationary) and nutrient store (egg cytoplasm).
Common mistakes
Do not give these marks away
- 01
Writing “it is adapted” without naming a structure and the job it helps with.
- 02
Putting chloroplasts in root hair cells, or saying xylem carries glucose.
- 03
Confusing the acrosome (enzymes) with mitochondria (energy transfer) in sperm.
Why do root hair cells contain many mitochondria?
ATo photosynthesise underground
BTo transfer energy for active transport of mineral ions
CTo store starch
DTo make cellulose for the leaf
Show the answer
To transfer energy for active transport of mineral ions. Nitrate and other ions are often taken up against a concentration gradient. Active transport needs energy from respiration in mitochondria. Root hairs do not photosynthesise.
Quick questions
If this is the bit you searched
What are specialised cells in GCSE Biology?
Cells that have differentiated so their structure matches one function, such as sperm, nerve, palisade and root hair cells.
How is a sperm cell adapted?
Streamlined shape, flagellum for swimming, many mitochondria for energy, and an acrosome of enzymes to digest the egg membrane.
How is a palisade cell adapted for photosynthesis?
It is column-shaped and packed with chloroplasts, and it sits near the top of the leaf to absorb maximum light.
What does a root hair cell absorb?
Water by osmosis and mineral ions by active transport. The long hair increases surface area; mitochondria supply energy for ion uptake.