1.3 Specialised cells
7 exam questions worth 17 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Which adaptation helps a root hair cell to absorb water from the soil?
Choose one answer.
Correct Not quite: the answer is A hair-like projection that gives a large surface area
Mark scheme
B (A hair-like projection that gives a large surface area)
Model answer
B: A hair-like projection that gives a large surface area. The hair increases the surface area, so more water can be absorbed.
A sperm cell has a tail and many mitochondria.
Explain how each of these adaptations helps the sperm cell.
Mark scheme
- the tail allows the sperm to swim to the egg (1)
- mitochondria release energy (by respiration) (1)
- for swimming / for the tail to move (1)
Model answer
The tail lets the sperm cell swim to the egg. The mitochondria release energy by respiration, and this energy is used to move the tail.
Describe how a nerve cell is adapted to carry electrical impulses from one part of the body to another.
Mark scheme
Any two from:
- it is very long, so it can carry impulses over long distances (1)
- it has branched ends / dendrites to connect to other nerve cells (1)
- it has an insulating sheath that speeds up the impulse (1)
Model answer
A nerve cell is very long, so one cell can carry an impulse a long way. Its branched ends connect it to other nerve cells.
Xylem cells carry water up a plant.
Explain how xylem cells are adapted for this job.
Mark scheme
- the cells are hollow / have no cytoplasm or nucleus / have no end walls (1)
- so water can flow through freely (1)
- walls are strengthened with lignin (1)
- so the tubes do not collapse / they support the plant (1)
- maximum 3 marks
Model answer
Xylem cells are dead and hollow, with no end walls, so they form a continuous tube that water can flow through freely. Their walls contain lignin, which makes them strong so the tubes do not collapse.
Phloem tubes have companion cells next to them. Companion cells contain many mitochondria.
Explain why.
Mark scheme
- mitochondria release energy (by respiration) (1)
- for moving (loading) sugars into the phloem tube / active transport (1)
Model answer
The mitochondria release energy by respiration. The energy is used to move sugars into the phloem tubes.
Ciliated epithelial cells line the airways to the lungs.
Describe how the cilia help to protect the lungs.
Mark scheme
- cilia beat / move (1)
- to move mucus (with trapped dust and microorganisms) away from the lungs (1)
Model answer
The cilia beat to sweep mucus, which has trapped dust and microorganisms, away from the lungs.
A human egg cell is much larger than a sperm cell.
Explain two ways in which the egg cell is adapted for its function.
Mark scheme
Any two adaptations, each with an explanation:
- the cytoplasm contains nutrients / a food store (1) to feed the embryo after fertilisation (1)
- the cell membrane changes structure after fertilisation (1) so no more sperm can enter (1)
- it has a haploid nucleus (1) so that, with the sperm's nucleus, the embryo has a full set of chromosomes (1)
Model answer
The egg cell's cytoplasm is full of nutrients, which feed the embryo in the first days after fertilisation. After one sperm has entered, the membrane of the egg changes, which stops other sperm getting in so that only one sperm fertilises the egg.
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