Link root hair cells with absorption from soil
Explain a surface extension without giving it a photosynthesis function.
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 the distinction between plant, animal and bacterial cells. Read the supplied evidence before drawing a conclusion.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which material is normally absorbed from soil by a root hair cell?
What you will learn
- Identify the root hair as a cell extension.
- Connect the extension with absorption of water and mineral ions.
A large contact surface
A root hair cell has a long extension from the root surface into the spaces between soil particles. This increases the surface area in contact with soil solution, supporting absorption of water and mineral ions. The hair is part of a cell, not a separate root organ.
The cell has a wall and membrane around its contents and a large vacuole. It usually lacks chloroplasts because it is underground and absorption is its specialised role. It is still a plant cell.
Make a precise explanation
An answer should identify absorption, name water and mineral ions, and connect the extension with a greater contact area. Saying the hair makes the root longer misses the cell-level mechanism. Transport mechanisms are studied in the following membrane-transport sections.
The diagram is schematic; the length of the drawn extension is not a measurement of a real root hair. Damaging hairs can reduce absorbing surface, but soil conditions and membrane activity also affect absorption, so a drawing cannot quantify a rate.
Sources for this lesson
Pause and explain
How does the root hair extension support its role?
Worked example
Why is a root hair cell better described as an absorption cell than a photosynthesis cell?
Show the worked solution
- Its extension increases soil contact area.
- It absorbs water and mineral ions.
- Its usual location and lack of chloroplasts do not support photosynthesis.
Answer It specialises in absorption through a large soil-contact surface.
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.
State the function of a root hair cell.
Give me a hint
Include the absorbed materials.
Compare my reasoning
- It absorbs water.
- It absorbs mineral ions from soil solution.
Absorption of water and mineral ions.
Look for these in your work
- Name both materials.
- Give the soil source.
A root cell has a long extension but no chloroplasts. Explain how it fits its function.
Give me a hint
Consider contact area and location.
Compare my reasoning
- Extension increases soil contact.
- Absorption does not require chloroplasts.
An absorption-specialised plant cell with increased soil contact area.
Look for these in your work
- Structure-function link.
- Retain plant-cell identity.
Two roots have equal length, but one has many intact hairs and the other few. Suggest a functional difference and one variable to control when testing it.
Give me a hint
Equal organ length does not ensure equal cell surface.
Compare my reasoning
- More hairs can give greater absorbing surface.
- Compare the same soil moisture or mineral concentration.
Potentially greater absorption with more intact hairs; control soil moisture or mineral concentration.
Look for these in your work
- Conditional prediction.
- Relevant controlled variable.
Common mistakes
- A root hair is a cell extension, not a separate organ.
- Lack of chloroplasts does not make it an animal cell.
What can you explain now?
Name two materials absorbed by root hair cells.
Compare with the explanation
Water and mineral ions.
The specialised function is absorption from soil solution.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain how an extension changes contact area without changing cell identity.
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.