Recognise a root hair cell and its uptake roles
Identify an epidermal-cell extension rather than a separate root or an animal hair.
Section B8.2 · Water uptake
Exam scope and assessment notes
Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.
Before you begin
- Recall plant cells, osmosis and active transport.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which boundary controls entry into a living cell?
What you will learn
- Identify a root hair cell in a diagram
- State its water and mineral-ion uptake roles
One cell with an extension
A root hair is a long, narrow extension of a root epidermal cell. It increases contact with soil solution. The cell has a wall, membrane, cytoplasm and a large vacuole; the hair is continuous with that cell rather than being a separate multicellular root branch.
Root hair cells absorb water and mineral ions. They usually occur behind the growing root tip in the appropriate root region, not as a covering of every point along every root.
Use the membrane and the whole cell
Water can enter by osmosis across the partially permeable membrane when the water-potential gradient favours entry. Mineral ions can be absorbed by transport proteins, including active transport against a concentration gradient. These mechanisms were studied separately in membrane transport.
A diagram’s long projection identifies the adaptation, but does not measure how much water entered. Root hairs are living cells; do not apply the “no cell contents” description of a mature xylem vessel to them.
Sources for this lesson
Pause and explain
What is a root hair?
Worked example
A diagram shows a living epidermal cell with one long projection into soil. Identify it and its two uptake roles.
Show the worked solution
- The projection belongs to one epidermal cell, so it is a root hair cell.
- State water and mineral-ion absorption.
Answer A root hair cell absorbs water and mineral ions from soil solution.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Name the long projection on the supplied root epidermal-cell model and two substances taken up.
Give me a hint
Connect the outside structure with the soil solution.
Compare my reasoning
- Identify the projection as a root hair.
- State water and mineral ions as the uptake materials.
Root hair; water and dissolved mineral ions are absorbed.
Look for these in your work
- Identify the cell extension
- Give both uptake materials
Correct “root hairs have no cytoplasm because they carry water”.
Give me a hint
Compare living uptake cells with mature conducting vessels.
Compare my reasoning
- Root hair cells are living and contain cytoplasm.
- Mature xylem vessels lack contents, but that is a different structure.
Root hair cells contain cytoplasm and absorb water/mineral ions; absent contents describe mature xylem vessels, not root hairs.
Look for these in your work
- Distinguish uptake from conduction
- Keep the two cell descriptions separate
A drawing has a thin single-cell projection and a branching structure with many cells. Which is a root hair, and why?
Give me a hint
Cell number separates the structures.
Compare my reasoning
- The single-cell extension fits a root hair.
- The multicellular branch is a root branch rather than one hair.
The thin single-cell projection is the root hair; the many-celled branch is a different structure.
Look for these in your work
- Use cell continuity
- Reject a shape-only branch comparison
Common mistakes
- Calling the projection a multicellular lateral root.
- Describing root hair cells as empty dead xylem vessels.
What can you explain now?
What is a root hair?
Compare with the explanation
An extension of one root epidermal cell
It remains part of a single living cell.
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Make it stick
Draw one root hair cell and label its membrane, wall and long extension.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.