ENZYMES
NAME:
MULTIPLE CHOICE QUESTION:
1. Lactase is a human enzyme that catalyses the breakdown of lactose in milk.
At which temperature does lactase work fastest?
A 0 °C B 18 °C C 37 °C D 100 °C
2. The list shows some statements about enzymes.
1 They all contain the element nitrogen.
2 They are proteins.
3 They can be denatured by cold temperatures.
4 Their specificity is due to the complementary shapes of the active site and the substrate.
Which statements are correct?
A 1, 2 and 3 B 1, 2 and 4 C 2 and 4 only D 3 and 4
3. What is a characteristic of all catalysts?
A They are broken down in the reaction. B They are made of protein.
C They are not changed by the reaction. D They do not change the rate of the reaction.
4. A student eats a bread roll. Why does salivary amylase stop working in the stomach?
A All the amylase has been used up.
B All the starch has been converted to glucose.
C Amylase cannot work in acid conditions.
D The temperature in the stomach is higher than in the mouth.
5. Amylase and pepsin are digestive enzymes. The shapes of their active sites are different.
What causes the difference in the shapes of their active sites?
A They are produced by different parts of the digestive system.
B They have different pH ranges.
C They contain different sequences of amino acids.
D They are made of different proportions of the bases A, T, C and G.
6. Starch is digested by amylase in the mouth, but it is not digested in the stomach.
What is the reason for this?
A All starch digestion is completed in the mouth.
B The pH in the stomach is not suitable for the amylase to work.
C The starch does not stay in the stomach long enough to be digested.
D The temperature in the stomach is not suitable for the amylase to work.
7. Which are characteristics of enzymes?
A They are carbohydrates and biological catalysts.
B They are carbohydrates and chemical messengers.
C They are proteins and biological catalysts.
D They are proteins and chemical messengers.
8. Which statement about enzymes is essential to the lock and key hypothesis?
A Enzyme molecules are catalysts.
B Enzyme molecules can be damaged by high pH values.
C Enzyme molecules can be damaged by high temperatures.
D Enzyme molecules each have a distinct shape.
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,9. A human digestive enzyme breaks down its substrate at a fast rate at 35°C.
What would occur if the enzyme and substrate were kept at 75°C?
A The enzyme would stop working and be denatured.
B The reaction would continue at the same rate.
C The reaction would take place more quickly.
D The reaction would take place more slowly.
10. Which statement is correct?
A The active site of an enzyme has the same shape as the substrate.
B The active site is not affected by changes in temperature.
C The shape of the active site of an enzyme is complementary to its substrate.
D The substrate and product combine at the active site.
11. Which description of an enzyme-catalysed reaction is correct?
A The substrate binds to an enzyme with the same shape and a product is formed.
B The product binds to an enzyme with the same shape and a substrate is formed.
C The product binds to an enzyme with a complementary shape and a substrate is formed.
D The substrate binds to an enzyme with a complementary shape and a product is formed.
12. Two enzyme-controlled reactions are shown.
From these reactions, what deduction can be made about enzymes?
A Enzyme 1 has been changed to enzyme 2.
B Enzyme 2 slows down the production of amino acids.
C Enzymes can build up large molecules.
D Enzymes only break down large molecules.
13. The diagram represents a protein molecule.
What do the small circles represent?
A amino acids B fatty acids
C glycerol D simple sugars
14. The diagram shows the action of amylase.
What is the function of the enzyme amylase?
A breaks down the substrate into amino acids
B changes the product into the substrate
C increases the rate of starch breaking down into glucose
D increases the rate of starch breaking down into maltose
15. The diagram represents enzyme action.
What are parts W, X and Y in this chemical reaction?
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,16. Which diagram of an enzyme, active site and substrate is correct?
17. This sequence of diagrams shows how an enzyme works.
Which labelled part is the active site?
AP BQ
CR DS
18. The diagrams represent an enzyme molecule and its substrate.
Which diagram shows these molecules after they are heated to 100oC?
19. The diagrams represent an enzyme and its substrate.
Which part of the enzyme molecule is the active site for this substrate?
20. The diagram represents stages in the breakdown of starch to maltose by the enzyme amylase.
21. In an enzyme action, where is the active site and where are the lock and the key?
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, 22. Starch is digested to maltose by the enzyme amylase. According to the ‘lock and key’ hypothesis,
which is the ‘key’ and which is the ‘lock’?
23. Protease breaks down proteins into amino acids. In the ‘lock and key’ hypothesis, what is the lock
and what is the key?
24. The table shows the temperature and pH at which four different enzymes are most active. Which
enzyme is a protease from the stomach?
25. Enzyme X digests starch in the duodenum.
The same volumes of starch suspension and enzyme X were put into four test-tubes, A, B, C and D.
Each test-tube was kept at a different pH and temperature, as shown in the table.
In which test-tube will starch digestion be the quickest?
26. A student investigates the breakdown of fats in milk by lipase. Four test-tubes labelled A, B, C and D
are set up.
The table shows the contents of each test-tube.
In which test-tube will the contents become acidic most quickly?
27. A student wrote some notes about enzymes. She wrote:
‘The …1… of an enzyme is …2… to an area on the substrate.
This area on the substrate can fit into it to form an …3… complex’.
Which words correctly complete gaps 1, 2 and 3?
10
NAME:
MULTIPLE CHOICE QUESTION:
1. Lactase is a human enzyme that catalyses the breakdown of lactose in milk.
At which temperature does lactase work fastest?
A 0 °C B 18 °C C 37 °C D 100 °C
2. The list shows some statements about enzymes.
1 They all contain the element nitrogen.
2 They are proteins.
3 They can be denatured by cold temperatures.
4 Their specificity is due to the complementary shapes of the active site and the substrate.
Which statements are correct?
A 1, 2 and 3 B 1, 2 and 4 C 2 and 4 only D 3 and 4
3. What is a characteristic of all catalysts?
A They are broken down in the reaction. B They are made of protein.
C They are not changed by the reaction. D They do not change the rate of the reaction.
4. A student eats a bread roll. Why does salivary amylase stop working in the stomach?
A All the amylase has been used up.
B All the starch has been converted to glucose.
C Amylase cannot work in acid conditions.
D The temperature in the stomach is higher than in the mouth.
5. Amylase and pepsin are digestive enzymes. The shapes of their active sites are different.
What causes the difference in the shapes of their active sites?
A They are produced by different parts of the digestive system.
B They have different pH ranges.
C They contain different sequences of amino acids.
D They are made of different proportions of the bases A, T, C and G.
6. Starch is digested by amylase in the mouth, but it is not digested in the stomach.
What is the reason for this?
A All starch digestion is completed in the mouth.
B The pH in the stomach is not suitable for the amylase to work.
C The starch does not stay in the stomach long enough to be digested.
D The temperature in the stomach is not suitable for the amylase to work.
7. Which are characteristics of enzymes?
A They are carbohydrates and biological catalysts.
B They are carbohydrates and chemical messengers.
C They are proteins and biological catalysts.
D They are proteins and chemical messengers.
8. Which statement about enzymes is essential to the lock and key hypothesis?
A Enzyme molecules are catalysts.
B Enzyme molecules can be damaged by high pH values.
C Enzyme molecules can be damaged by high temperatures.
D Enzyme molecules each have a distinct shape.
10
,9. A human digestive enzyme breaks down its substrate at a fast rate at 35°C.
What would occur if the enzyme and substrate were kept at 75°C?
A The enzyme would stop working and be denatured.
B The reaction would continue at the same rate.
C The reaction would take place more quickly.
D The reaction would take place more slowly.
10. Which statement is correct?
A The active site of an enzyme has the same shape as the substrate.
B The active site is not affected by changes in temperature.
C The shape of the active site of an enzyme is complementary to its substrate.
D The substrate and product combine at the active site.
11. Which description of an enzyme-catalysed reaction is correct?
A The substrate binds to an enzyme with the same shape and a product is formed.
B The product binds to an enzyme with the same shape and a substrate is formed.
C The product binds to an enzyme with a complementary shape and a substrate is formed.
D The substrate binds to an enzyme with a complementary shape and a product is formed.
12. Two enzyme-controlled reactions are shown.
From these reactions, what deduction can be made about enzymes?
A Enzyme 1 has been changed to enzyme 2.
B Enzyme 2 slows down the production of amino acids.
C Enzymes can build up large molecules.
D Enzymes only break down large molecules.
13. The diagram represents a protein molecule.
What do the small circles represent?
A amino acids B fatty acids
C glycerol D simple sugars
14. The diagram shows the action of amylase.
What is the function of the enzyme amylase?
A breaks down the substrate into amino acids
B changes the product into the substrate
C increases the rate of starch breaking down into glucose
D increases the rate of starch breaking down into maltose
15. The diagram represents enzyme action.
What are parts W, X and Y in this chemical reaction?
10
,16. Which diagram of an enzyme, active site and substrate is correct?
17. This sequence of diagrams shows how an enzyme works.
Which labelled part is the active site?
AP BQ
CR DS
18. The diagrams represent an enzyme molecule and its substrate.
Which diagram shows these molecules after they are heated to 100oC?
19. The diagrams represent an enzyme and its substrate.
Which part of the enzyme molecule is the active site for this substrate?
20. The diagram represents stages in the breakdown of starch to maltose by the enzyme amylase.
21. In an enzyme action, where is the active site and where are the lock and the key?
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, 22. Starch is digested to maltose by the enzyme amylase. According to the ‘lock and key’ hypothesis,
which is the ‘key’ and which is the ‘lock’?
23. Protease breaks down proteins into amino acids. In the ‘lock and key’ hypothesis, what is the lock
and what is the key?
24. The table shows the temperature and pH at which four different enzymes are most active. Which
enzyme is a protease from the stomach?
25. Enzyme X digests starch in the duodenum.
The same volumes of starch suspension and enzyme X were put into four test-tubes, A, B, C and D.
Each test-tube was kept at a different pH and temperature, as shown in the table.
In which test-tube will starch digestion be the quickest?
26. A student investigates the breakdown of fats in milk by lipase. Four test-tubes labelled A, B, C and D
are set up.
The table shows the contents of each test-tube.
In which test-tube will the contents become acidic most quickly?
27. A student wrote some notes about enzymes. She wrote:
‘The …1… of an enzyme is …2… to an area on the substrate.
This area on the substrate can fit into it to form an …3… complex’.
Which words correctly complete gaps 1, 2 and 3?
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