How does water enter a root hair cell?
Reveal answer
Soil water more dilute than cell sap → water moves in by osmosis across the partially permeable membrane.
Key words: osmosis
3(h) TRANSPORT · RECALL
3.5B Water absorption by root hair cells
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Which feature of a root hair cell gives a large surface area?
Reveal answer
The long, thin root hair extension.
Key words: hair
How do root hairs take in mineral ions?
Reveal answer
Ions at lower concentration in soil → active transport using energy from respiration.
Key words: active transport
Why does waterlogging reduce ion uptake?
Reveal answer
Less oxygen in soil → less aerobic respiration → less energy for active transport.
Key words: oxygen · active
Why does too much fertiliser make plants wilt?
Reveal answer
Soil water becomes more concentrated → water leaves roots by osmosis → cells flaccid.
Key words: osmosis
Why do root hair cells contain many mitochondria?
Reveal answer
To release energy by respiration for active transport.
Key words: active transport
How does water cross the root to the xylem?
Reveal answer
Cell to cell by osmosis → across cortex → into xylem.
Key words: osmosis · xylem
What is meant by the term root hair cell?
Reveal answer
Epidermal root cell with a projection that increases absorption area.
Key words: root hair cell
Water and mineral uptake: for Main process, give the water and the mineral ions.
Reveal answer
Water: Osmosis. Mineral ions: Diffusion or active transport.
Key words: Main process
Water and mineral uptake: for Membrane requirement, give the water and the mineral ions.
Reveal answer
Water: Partially permeable membrane. Mineral ions: Specific carrier/channel proteins.
Key words: Membrane requirement
Water and mineral uptake: for Energy, give the water and the mineral ions.
Reveal answer
Water: No direct ATP use. Mineral ions: Active uptake requires ATP.
Key words: Energy
Water and mineral uptake: for Gradient, give the water and the mineral ions.
Reveal answer
Water: Down water-potential gradient. Mineral ions: Can move against concentration gradient.
Key words: Gradient
True or false, and why? “Roots suck water from soil.”
Reveal answer
False. Water crosses root-hair membranes by osmosis down a water-potential gradient.
True or false, and why? “Osmosis uses energy from respiration.”
Reveal answer
False. It is passive; respiration powers active ion transport.
True or false, and why? “Root hairs are tiny roots.”
Reveal answer
False. Each is a projection from one epidermal cell.