Question 1
Which shows the products of the digestion of fats and oils by lipase?
- Amino acids
- Fatty acids and glycerol
- Simple reducing sugars
- Maltose and glucose
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Answer: B
Question 2
(a) Describe what is meant by chemical digestion. [2] (b) Explain why the products of chemical digestion can be absorbed into the blood. [1]
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- (a) breakdown of large molecules (1)
- insoluble molecules into small soluble molecules (1)
- (b) they are small and soluble / can pass through the gut wall (1)
Question 3
Complete the table for the three digestive enzymes.
| Enzyme | Substrate | Product | Where secreted |
|---|---|---|---|
| Amylase | |||
| Protease | |||
| Lipase |
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- amylase: starch (1)
- amylase: simple (reducing) sugars (1) allow maltose; ignore sugar unqualified
- amylase: salivary glands / pancreas (1)
- protease: protein and amino acids (1)
- protease: stomach / pancreas (1)
- lipase: fats and oils and fatty acids and glycerol (1)
- lipase: pancreas (1)
- Max 6
Question 4
Describe two functions of hydrochloric acid in gastric juice.
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- kills harmful microorganisms / bacteria in food (1)
- provides an acidic pH for optimum enzyme (protease / pepsin) activity (1)
Question 5
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanDescribe the digestion of starch in the digestive system.
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- amylase (from salivary glands / pancreas) (1)
- breaks starch down to maltose (1)
- maltase breaks maltose down to glucose (1)
- maltase is on the membranes of epithelium lining the small intestine (1)
Question 6
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels mean(a) Name the protease that works in the stomach. [1] (b) Explain why the same protease does not work in the small intestine. [2] (c) Name the protease that works in the small intestine and state the pH conditions it needs. [2]
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- (a) pepsin (1)
- (b) stomach is acidic, small intestine is alkaline (1)
- pepsin works (best) in acidic conditions / alkaline pH is not its optimum (1) allow pepsin is denatured in alkaline conditions
- (c) trypsin (1)
- alkaline (conditions) (1)
Question 7
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanAcidic food and gastric juice enter the duodenum from the stomach. Which substance makes the contents of the duodenum suitable for enzymes to work?
- Amylase
- Hydrochloric acid
- Bile
- Glycerol
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Answer: C (bile; it is alkaline and neutralises the acid)