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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Key diagram
A root hair cell has a long, thin root hair extension that increases surface area for absorbing water by osmosis and mineral ions by active transport. It has many mitochondria and a large vacuole.
The root hair cell is a favourite specialised-cell question because it links cell structure to two different transport processes: osmosis for water and active transport for mineral ions. Students must draw the extension clearly and explain both absorption mechanisms.
Drawing the root hair cell
Draw a rectangular cell body with a long, thin projection extending outward from one side: this is the root hair. The projection should be much longer than the cell body is wide. Inside, draw a large central vacuole extending partly into the root hair. Place the nucleus to one side and scatter many small mitochondria throughout the cytoplasm.
Show the root hair projecting between soil particles (draw small irregular shapes around it) to illustrate its position in the soil.
Absorbing water by osmosis
The soil water has a higher water potential than the cell sap in the vacuole. Water moves into the root hair cell by osmosis through the partially permeable cell membrane. The large vacuole with concentrated cell sap maintains a low water potential inside the cell, sustaining the water-potential gradient.
The long root hair provides a large surface area in contact with soil water, increasing the rate of absorption.
Absorbing minerals by active transport
Mineral ions such as nitrate and magnesium are present in lower concentrations in the soil than inside the root hair cell. They must be absorbed against the concentration gradient by active transport, which requires energy from respiration. This is why the root hair cell has many mitochondria: they carry out aerobic respiration to release the energy needed for active transport.
Label checklist
Check these labels are present and correctly positioned before finishing your drawing.
✓Root hair (long extension)
✓Cell wall
✓Cell membrane
✓Cytoplasm
✓Nucleus
✓Large central vacuole
✓Mitochondria (many)
✓Soil particles (context)
Try a diagram question (4 marks)
Explain how the root hair cell is adapted for absorbing water and mineral ions. [4]
Show the answer and marking guidance
Long root hair increases the surface area in contact with soil water.
Large vacuole with concentrated cell sap maintains a water potential gradient, so water enters by osmosis.
Many mitochondria provide energy from respiration.
Energy is needed for active transport of mineral ions against the concentration gradient.
Original Cambridge-style practice written for this site.
Common diagram mistakes
Check these against your own drawing before moving on.
Drawing the root hair too short: it should clearly extend well beyond the cell body.
Saying minerals are absorbed by osmosis instead of active transport.
Forgetting to mention mitochondria when explaining active transport.
Writing "diffusion" instead of "osmosis" for water absorption.