Question 1
Which enzyme completes the digestion of starch to glucose?
- Amylase
- Maltase
- Protease
- Lipase
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Answer: B (1)
Question 2
(a) Explain why a builder needs more energy from his diet than an office worker of the same age. (2) (b) Explain why a pregnant woman needs more energy than before she was pregnant. (1)
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- the builder is more active / uses his muscles more (1)
- so more respiration is needed to release energy / his muscles contract more (1)
- extra energy is needed for the growth of the fetus (1) allow 'baby' for fetus
Question 3
State one function of each of these in the diet. (i) calcium (ii) iron (iii) vitamin D (iv) dietary fibre
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- calcium: for strong bones / teeth (1)
- iron: to make haemoglobin (1) allow to make red blood cells; to carry oxygen
- vitamin D: helps absorb calcium (1) allow for strong bones
- dietary fibre: provides bulk / helps food move through the gut / prevents constipation (1) do not accept 'provides energy'
Question 4
(a) Name the part of the alimentary canal where most water is absorbed from the remaining food. (1) (b) Describe how food is moved along the gut by peristalsis. (2)
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- large intestine / colon (1)
- circular muscles contract behind the food and squeeze it forward (1)
- waves of muscle contraction / contraction and relaxation of muscles move along the gut (1) ignore 'muscles push food' without reference to contraction
Question 5
(a) Name the enzyme that digests lipids and give the products of digestion. (2) (b) Explain how bile helps the digestion of lipids. (2)
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- lipase (1)
- fatty acids and glycerol (1)
- bile emulsifies lipid / breaks lipid into small droplets (1) so the surface area is bigger for lipase to work (1)
- allow neutralises stomach acid so the pH is right for lipase (1) as an alternative to either mark in (b), max 2 for (b)
Question 6
Biology only (what this means)
Biology only: only in International GCSE Biology. Double Award students can skip it. What the labels meanA student burned 0.8 g of a food sample under a boiling tube containing 25 g of water. The temperature of the water rose from 20 °C to 36 °C. Calculate the energy released per gram of the food. The energy needed to raise the temperature of 1 g of water by 1 °C is 4.2 J.
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- temperature change = 16 °C and energy released = 25 × 4.2 × 16 (1)
- = 1680 J (1)
- 1680 ÷ 0.8 = 2100 J/g (1) allow 3 marks for the correct final answer. Allow error carried forward from the energy released.
Question 7
Explain how the small intestine is adapted for the absorption of the products of digestion.
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| Level | Marks | What the answer does |
|---|---|---|
| 3 | 5–6 | A clear, well-structured explanation covering at least four adaptations, including the structure of a villus, each linked to a reason (surface area, diffusion distance, concentration gradient). Scientific terms are used correctly. |
| 2 | 3–4 | An explanation of at least two adaptations, with reasons given for most. Some links to absorption are incomplete. |
| 1 | 1–2 | A limited answer that names one or two features, such as villi or capillaries, with little or no explanation. |
Indicative content
- small intestine is long, and its wall is folded, giving a large surface area
- wall is covered in villi, and villi have microvilli, which increases surface area further
- epithelium of the villus is one cell thick, so there is a short diffusion distance
- network of blood capillaries in each villus carries absorbed glucose and amino acids away
- this keeps a steep concentration gradient so absorption continues by diffusion (and active transport)
- lacteal in the centre of each villus absorbs fatty acids and glycerol