Original practice · 5 questions · 16 marks · about 18 minutes

Digestive Enzymes Practice Questions

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These questions test your knowledge of the main digestive enzymes, where they work, what they break down, and the conditions they need.

1. Question 1

   Paper 2 Both 4 marks Difficulty 2/5

   Copy and complete the table for the three main groups of digestive enzymes: name the substrate and product for each. | Enzyme group | Substrate | Product | |---|---|---| | Amylase |? |? | | Protease |? |? | | Lipase |? |? |

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   1. Amylase: substrate = starch; product = maltose (a reducing sugar).
   2. Protease: substrate = protein; product = amino acids.
   3. Lipase: substrate = lipids/fats; product = fatty acids and glycerol.
   4. All three processes are hydrolysis reactions (water is used to break bonds).

2. Question 2

   Paper 4 Both 3 marks Difficulty 3/5

   Explain the role of bile in digestion and state where bile is produced and stored.

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   1. Bile is produced in the liver and stored in the gall bladder.
   2. Bile emulsifies fats: breaks large fat droplets into smaller droplets.
   3. This increases the surface area for lipase to act on, speeding up fat digestion.

   Watch for: Saying bile "digests" fat: bile does not contain enzymes; it emulsifies fat.

3. Question 3

   Paper 4 Extended 3 marks Difficulty 3/5

   Pepsin is a protease found in the stomach. Explain why hydrochloric acid in gastric juice is important for pepsin function.

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   1. HCl provides the acidic conditions (pH 1.5–2) that pepsin needs.
   2. pH 2 is the optimum pH for pepsin: it works most efficiently here.
   3. HCl also kills bacteria in food, providing a first line of defence.

4. Question 4

   Paper 2 Core 2 marks Difficulty 1/5

   Name the organ where amylase first begins to digest starch.

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   1. The mouth.
   2. Salivary amylase is produced by the salivary glands.

5. Question 5

   Paper 4 Extended 4 marks Difficulty 4/5

   The pancreas produces amylase, protease, and lipase. Explain why the pancreas is described as the most important digestive gland and describe the conditions in the duodenum where these enzymes work.

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   1. The pancreas produces all three enzyme types: it can digest carbohydrates, proteins, and fats.
   2. Pancreatic juice is released into the duodenum (first part of small intestine).
   3. The duodenum has an alkaline pH (due to bile and sodium hydrogencarbonate).
   4. This is the optimum pH for pancreatic enzymes (around pH 7–8).