AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Root hair cells are adapted for the efficient uptake of water by osmosis,…
Full specification wording
Plant organ system: Root hair cells are adapted for the efficient uptake of water by osmosis, and mineral ions by active transport.
Root hair cells are specialised cells on the surface of roots.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 7 of 13
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Root hair cells are specialised cells on the surface of roots. Each has a long, thin extension that increases the surface area for absorption. Water enters by osmosis because the water potential inside the root hair cell is lower than in the soil solution, so water moves across the partially permeable membrane from a dilute solution to a more concentrated solution. Mineral ions are absorbed by active transport, which uses energy from respiration to move ions against their concentration gradient, from a lower concentration in the soil to a higher concentration inside the cell. The large number of mitochondria in root hair cells supplies the energy needed for active transport.
What earns the marks
- Describe the long, thin extension of a root hair cell as an adaptation that increases surface area for absorption.
- State that water enters root hair cells by osmosis through the partially permeable membrane.
- Explain that osmosis moves water from a dilute solution in the soil to a more concentrated solution inside the cell.
- State that mineral ions are absorbed by active transport, which requires energy from respiration.
- Explain that active transport moves mineral ions against a concentration gradient, from lower concentration in the soil to higher concentration in the cell.
- Link the presence of many mitochondria in root hair cells to the energy supply for active transport.
Common mistakes and how to put them right
Stating that mineral ions enter by osmosis.
Put it right: State that mineral ions are absorbed by active transport.
Saying that active transport does not require energy.
Put it right: State that active transport uses energy released by respiration.
Describing water movement as from a concentrated solution to a dilute solution.
Put it right: State that water moves from a dilute solution to a more concentrated solution.
Ignoring the surface area adaptation.
Put it right: Explain that the long extension increases the surface area for uptake.
Exam tips
- Name the process for each substance: osmosis for water and active transport for mineral ions.
- When explaining active transport, state the direction of movement against the concentration gradient and the need for energy.
- Link the structure of the root hair cell to its function in one sentence, for example the long extension increases surface area for absorption.
Try the lesson
The start of the Plant organ system: Root hair cells are adapted for the efficient uptake of water by osmosis, and mineral ions by active transport. lesson, made from checked teaching notes for this specification point.
Have a go first
By which process do root hair cells take in water from the soil?
Listen
Root hair cells are specialised cells on the surface of roots. Each has a long, thin extension that increases the surface area for absorption. Water enters by osmosis because the water potential inside the root hair cell is lower than in the soil solution, so water moves across the partially permeable membrane from a dilute solution to a more concentrated solution. Mineral ions are absorbed by active transport, which uses energy from respiration to move ions against their concentration gradient, from a lower concentration in the soil to a higher concentration inside the cell. The large number of mitochondria in root hair cells supplies the energy needed for active transport. A strong answer earns marks for these points. Describe the long, thin extension of a root hair cell as an adaptation that increases surface area for absorption. State that water enters root hair cells by osmosis through the partially permeable membrane. Explain that osmosis moves water from a dilute solution in the soil to a more concentrated solution inside the cell. State that mineral ions are absorbed by active transport, which requires energy from respiration. A common slip: Stating that mineral ions enter by osmosis. Instead, state that mineral ions are absorbed by active transport. Exam tip: Name the process for each substance: osmosis for water and active transport for mineral ions.
See it
Key words
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Adaptations of root hair cells
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Water uptake by osmosis
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Mineral ion uptake by active transport
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Energy from respiration for active transport
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See every definition
- Adaptations of root hair cells
- A long, thin extension increases the surface area for absorption, and a large number of mitochondria supplies the energy needed for active transport.
- Water uptake by osmosis
- Water moves across the partially permeable membrane from a dilute solution in the soil to a more concentrated solution inside the cell.
- Mineral ion uptake by active transport
- Ions are moved against their concentration gradient, from a lower concentration in the soil to a higher concentration inside the cell.
- Energy from respiration for active transport
- Active transport uses energy from respiration, and the large number of mitochondria in root hair cells supplies the energy needed.
Label the diagram
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