Explain why root hair cells are well adapted for the uptake of water from the soil.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Root hair cells have a very large surface area relative to their volume, which increases the rate of osmosis and therefore water uptake.
They have a thin cell wall, which reduces the diffusion distance for water molecules.
Water enters the root hair cells by osmosis because the water potential inside the cell is lower than that of the surrounding soil solution, so water moves into the cell.
They have a thin cell wall, which reduces the diffusion distance for water molecules.
Water enters the root hair cells by osmosis because the water potential inside the cell is lower than that of the surrounding soil solution, so water moves into the cell.
Examiner tips
- Mention both large surface area and thin cell wall; link each to increased water uptake. Explain osmosis and lower water potential. Use the exact terms "surface area", "diffusion distance", "water potential".
- common_mistakes
- :
- Failing to state that water potential is lower inside the cell. Using vague terms like "more water" instead of "osmosis". Omitting the thin cell wall or surface area points.
Mark scheme (4 marks)
- Root hair cells have a large surface area
- Large surface area increases the rate of osmosis / water uptake
- Root hair cells have a thin cell wall, reducing the diffusion distance
- Water enters by osmosis because the root hair cell has a lower water potential than the soil solution / soil water
Key terms in this question
Related
- All Cambridge International IGCSE Biology (0610) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →