1[1 mark]
What is the function of platelets?
- To carry oxygen
- To engulf pathogens
- To help the blood to clot
- To produce antibodies
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Answer: C C (to help the blood to clot)
2[3 marks]
Explain how the structure of a red blood cell is related to its function.
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- biconcave disc shape gives a large surface area (for absorbing oxygen) (1)
- contains haemoglobin which combines with oxygen (1)
- no nucleus so there is more room for haemoglobin (1)
3[4 marks]
Describe how phagocytes and lymphocytes protect the body against pathogens.
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- phagocytes engulf pathogens (1)
- and digest them (1)
- lymphocytes produce antibodies (1)
- which destroy pathogens (1) allow bind to pathogens
4[2 marks]
State two substances that are transported in the blood plasma.
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- carbon dioxide / urea / digested food molecules (glucose, amino acids) / mineral ions / hormones (1) ignore heat; do not accept oxygen or red blood cells
- any second different substance from the same list (1)
- Max 2
5
Higher tier
[2 marks]A blood sample has 5 × 10⁶ red blood cells in each mm³. Calculate the number of red blood cells in 3 mm³ of this blood. Give your answer in standard form.
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- 3 × 5 × 10⁶ = 15 × 10⁶ / 15 000 000 (1)
- 1.5 × 10⁷ (1)
6[3 marks]
Explain how the structure of an artery is related to its function.
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- thick muscular wall to withstand high pressure (1)
- elastic fibres allow the wall to stretch and spring back (1)
- narrow lumen helps maintain high pressure (1)
- Max 3
7[3 marks]
Explain how the structure of a capillary is related to its function.
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- walls are one cell thick (1)
- so there is a short diffusion distance (1)
- narrow and forms a large network, giving a large surface area for exchange with cells (1)