1[1 mark]
Which feature of a root hair cell gives it a large surface area?
- A thin cell wall
- Many mitochondria
- A long, thin projection
- A permanent vacuole
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Answer: C C
2[4 marks]
Explain two ways in which a root hair cell is adapted to absorb water and mineral ions. (4)
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- has a long thin projection / root hair (1)
- gives a large surface area for absorption (1)
- has many mitochondria (1)
- to release energy by respiration for active transport of mineral ions (1)
- has a thin cell wall (1)
- short distance for water / mineral ions to cross (1)
- cell sap is more concentrated than the soil water (1)
- so water enters by osmosis (1)
- Max 4: award each explanation mark only when linked to its adaptation
3[1 mark]
Which statement about the xylem is correct?
- It is made of living cells that carry sucrose
- It is made of lignified dead cells that carry water
- It is made of lignified living cells that carry sucrose
- It is made of dead cells that carry sucrose
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Answer: B B
4[3 marks]
Compare the structure and function of xylem and phloem. (3)
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- xylem is made of dead cells whereas phloem is made of living cells (1)
- xylem carries water and mineral ions whereas phloem carries sucrose (1)
- xylem walls are lignified whereas phloem cells have sieve plates / companion cells (1) allow phloem needs energy but xylem does not
5[4 marks]
Describe how water moves from the soil to the air through a plant. (4)
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- water enters the root hair cells (by osmosis) (1)
- water moves up through the xylem (1)
- water evaporates from the (surface of) cells in the leaf (1)
- water vapour diffuses out through the stomata (1)
6[2 marks]
A plant is short of water. Explain why its stomata close. (2)
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- guard cells lose water / become limp (1)
- reduces water loss by transpiration / evaporation (1) allow stops the plant drying out
7[3 marks]
Describe translocation and explain why it requires energy. (3)
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- transport of sucrose (1)
- from the leaves to the parts of the plant that use or store it / to growing regions (1) allow in the phloem
- phloem is made of living cells that use energy from respiration (1)
8[6 marks]
Explain how the structures of the xylem and the phloem are adapted to their functions in a plant. (6)
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| Level | Marks | What the answer does |
|---|---|---|
| 3 | 5–6 | A detailed explanation covering both tissues, linking structure to function for each, including lignin and dead cells in xylem and living cells using energy in phloem. Scientific terms are used accurately. |
| 2 | 3–4 | Some correct structures are linked to the function of both tissues, or a detailed explanation of one tissue and a limited one of the other. |
| 1 | 1–2 | Simple statements about what xylem and phloem carry, with little or no link to structure. |
Indicative content
- xylem carries water and mineral ions from the roots to the rest of the plant
- xylem cells are dead, with no cytoplasm or end walls, forming a continuous hollow tube so water flows easily
- walls are lignified, which strengthens them and stops the tubes from collapsing / supports the plant
- phloem carries sucrose (translocation) around the plant
- phloem is made of living cells, which use energy from respiration to transport sucrose
- sieve plates (holes in the end walls) allow sucrose to move from cell to cell
- companion cells have many mitochondria to release the energy needed