Topic 4: Enzymes and metabolism

1. An enzyme is aA. living molecule produced by glands to digest food in the alimentary canal.B. living molecule produced by cells to synthesise complex molecules from simpler ones.C. protein molecule produced by living cells to catalyse a particular biochemical reaction.D. protein molecule produced by living cells to catalyse a particular biochemical reaction at

37oC

2. An enzyme is only required in a small amount because

A. its shape is specific.

B. it speeds up both forward and backward reactions.

C. it is made of proteins.

D. it is not consumed in the reaction.

3. Which of the following can cause denaturation of enzymes?(1) high temperature(2) low temperature(3) presence of a competitive inhibitor

A.(1) onlyB.(1) and (2) onlyC.(1) and (3) onlyD.(1), (2) and (3)

4. Enzymes can be denatured by heat because they

A. Need optimal temperature to work

B. Are active in cold only

C. Are structurally changed in high temperature

D. Are biological catalysts

5. Which statement is true for all enzymes?

A. They are denatured at Temperature above 60℃

B. They catalyse the breakdown of larger molecules into smaller one

C. They have active sites which can bind to only one kind of substrate molecule

D. They reduce the amount of energy required to start a reaction.

6. Life is maintained by metabolism which refers to all

A. Breaking down reactions in the cells

B. Building up reactions in the cells

C. Essential biochemical reactions in the cells

D. Food oxidation and energy releasing processes in the cells

7. Which of the following cannot increase metabolic rate?

A. Reading

B. Sleeping

C. Talking

D. Jogging

8. Which property of enzymes can be explained by the lock-and-key hypothesis?

A. Enzymes are reusable.

B. Enzymes are proteins.

C. The actions of enzymes are specific.

D. Enzymes are biological catalysts.

Directions: Questions 9 to 11 refer to the diagram below, which shows the molecules before and after an

enzymatic reaction:

Before reaction After reaction

P

Q

R S T

9. What are molecules P to T?P Q R S T

A substrate enzyme substrate enzyme product

B product enzyme enzyme substrate substrate

C enzyme substrate substrate enzyme product

D enzyme substrate enzyme product product

10. Which of the following statements is/are correct?

(1) The specificity of the action of P can be explained by the lock-and-key hypothesis.

(2) P and R represent the lock in the lock-and-key hypothesis.

(3) Q, S and T represent the key in the lock-and-key hypothesis.

A. (1) only

B. (1) and (2) only

C. (2) and (3) only

D. (1), (2) and (3)

11. The reaction is an example of

(1) metabolism.

(2) catabolism.

(3) anabolism.

A. (1) and (2) only

B. (1) and (3) only

C. (2) and (3) only

D. (1), (2) and (3)

12. Which of the following are examples of catabolism?

(1) amino acid --> protein

(2) glucose --> water + carbon dioxide

(3) lipid --> glycerol + fatty acid

A. (1) and (2) only

B. (1) and (3) only

C. (2) and (3) only

D. (1), (2) and (3)

13. Amylase is an enzyme which catalyses the breakdown of starch to sugar. However, it cannot catalyse

the breakdown of cellulose. This is because

A. amylase is denatured by cellulose.

B. amylase can only work in a narrow range of pH.

C. amylase has a specific active site.

D. cellulose is an inhibitor to the action of amylase.

14. Which of the following is/are possible substrate(s) for enzyme X?

active sites

enzyme X

(1)

(2)

(3)

A. (1) only

B. (1) and (2) only

C. (1) and (3) only

D. (1), (2) and (3)

15. In an investigation of the effect of temperature on the enzyme activity, four test tubes containing an

enzyme solution and some milk were kept in water baths of different temperatures. The time taken for the

milk to coagulate was recorded. The results are shown in the table below.

Temperature of water bath (°C) 10 20 30 40

Time taken for coagulation of milk (min) X 7.0 4.0 1.5

‘X’ denotes no coagulation after 30 minutes.

What can be concluded from the results?

(1) The activity of this enzyme is affected by temperature.

(2) The optimum temperature for this enzyme is 40°C.

(3) This enzyme is denatured at high temperatures.

A (1) only

B (2) only

C (1) and (2) only

D (1), (2) and (3)

Directions: Questions 16 to 18 refer to the diagram below which shows an experiment. Equal volumes of

amylase solution were added to each of the four test tubes. All the tubes were kept at 40oC and the

contents were maintained at pH 7.

16. Which of the following is the factor being investigated?A. pHB. enzymeC. temperatureD. substrate

17. Which of the following is the conclusion of this experiment?A. Amylase works best at 40oC.B. Amylase can digest all the food substances except egg white.C. Amylase is specific to its substrate.D. Amylase works best at pH 7.

18. If lipase were used instead of amylase, which tube would contain acidic contents after 30 minutes?A. WB. XC. YD. Z

19. Seeds produce some enzymes when they germinate. Which of the following is the main function of these enzymes?A. to synthesise starch from sugars for storage

W

cloudy egg white suspension

Y

clear sucrose solution

X

cloudy starch suspension

Z

clear cooking oil

W

cloudy egg white suspension

X

clear maltose solution

Y

clear sucrose solution

Z

clear cooking oil

amylase added to each tube

At the beginning

After 30 minutes

B. to increase the rate of water absorption in the root

C. to break down insoluble food into soluble forms

D. to carry out photosynthesis

20. When hydrogen peroxide solution is added to a wound for sterilization, bubbles evolve rapidly

from the wound. Which of the following is a correct explanation of the phenomenon?

A. The red blood cells contains catalase

B. The haemoglobin liberates oxygen.

C. The hydrogen peroxide increases the respiratory rate of the wounded tissues.

D. Carbon dioxide is evolved from the wounded tissue.

Directions: Questions 21-25 refer to the diagram below, which is a diagrammatic representation of an enzyme catalysed reaction.

21. Which of the following substances can be used again?

A. P

B. Q

C. R

D. S

22. Which of the following statement can be deduced from the diagram?(1) Enzyme action is specific.(2) The reaction is reversible.(3) Enzymes are inactive at low temperatures.A. (1) and (2) onlyB. (1) and (3) onlyC. (2) and (3) onlyD. (1), (2) and (3)

23. Which of the following is not explained by the diagram?

A. Enzymes can be reused.

B. Enzymes is specific

C. Enzymes reaction is reversible

D. Reaction rate is speeded up.

24. Which of the following enzymatic reactions can be represented by the diagram?

A. Formation of fat

P Q

P

R

Q

R

S

RR

S

B. formation of lactose

C. Formation of sucrose

D. Formation of protein

25. What would happen when an enzyme with an optimum pH of 8.5 is added to a solution with a pH of 4?(1) The enzyme may be denatured.

(2) The enzyme activity would be lower at pH 4 than pH 8.5.

(3) The enzyme activity would be the same at both pH values.A. (1) only

B. (1) and (2) only

C. (1) and (3) only

D. (2) and (3) only

26. A fresh potato was mashed and some extract of the mash was added to a starch solution. After 20 minutes, a r

educing sugar was detected in the mixture.

Which of the following control experiment(s) is (are) required to conclude that the extract contained an enzyme

that digest starch?

(1) Boil the extract before adding it into the starch solution

(2) Use water instead of extract

(3) The extract had to be tested with Benedict’s solution

A. (1) Only

B. (1) and (3) only

C. (2) and (3) only

D. (1), (2) and (3)

Directions: Questions 27-29 below refer to the apparatus below which is used to compare the activities of the

enzyme catalase extracted from different tissues. The action of catalase is as follow:

27. What are P, Q and R at the beginning of the experiment

P Q R

A. H2O2 H2O2 catalase

B. H2O2 H2O catalase

C. catalase H2O H2O2

D. catalyse H2O2 H2O

28. How can the reaction rate be measured?

A. Measure the amount of gas collected in the first 30 seconds

B. Measure the amount of gas collected when the reaction has completed.

C. Measure the amount of H2O2 left in the flask.

D. Measure the amount of water formed in the flask.

29. Which of the following is not a precaution of the experiment?

A. All joints must be air-tight

B. The amount of enzyme extracted added each time must be the same/

C. The amount of H2O2 used each time must be the same.

D. The tap must be kept open during experiment.

Directions: Questions 30 and 31 refer to the graph below which shows the rate of reactions catalysed by enzymes X, Y and Z over a range of pH values.

30. The rates of the reactions catalysed by enzymes X and Y are equal atA. pH 4.B. pH 5.5.C. pH 6.5.D. pH 7.

31. Which of the following is the most probable conclusion that can be drawn from the graph?(1) The optimum pH values for enzymes X, Y and Z are 4, 7 and 8.5 respectively.(2) Enzyme X is found in the stomach and enzyme Y is found in the mouth.(3) Enzyme Z is more active than enzyme X and enzyme Y.A. (1) onlyB. (1) and (2) onlyC. (1) and (3) onlyD. (1), (2) and (3)

enzyme X

enzyme Z

enzyme Y

101 2 3 4 98765

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Directions: Question 32-34 below refer to the following experiment which investigates the activities of the

enzyme catalase which can be found in the liver of man. It catalyses the following reaction:

Hydrogen peroxide water + oxygen

Catalase was added to 5cm3 hydrogen peroxide solution and the oxygen evolved in the first minute was

collected. The results are shown below.

Test tube Temperature( )℃ Volume of oxygen collected(cm3)

P 0 0

Q 10 5

R 20 10

S 60 0

32. What conclusions can be drawn from the above results?

A. The enzymes was destroyed at low and high temperatures.

B. For every 10 increase in temperature, the reaction rate was double.℃

C. The enzyme only worked at certain temperature range.

D. Reaction rate varied linearly with temperature.

33. If another temperature is to be tested, which temperature should be chosen to get the maximum amount of

oxygen?

A. 27℃

B. 30℃

C. 37℃

D. 42℃

34. If test tubes P and S were them immersed in a water bath of 20 , what would be the amount of oxygen℃

collected in the first minute?

P S

A. 0 cm3 0 cm3

B. 0 cm3 10 cm3

C. 10 cm3 0 cm3

D. 10 cm3 10 cm3

catalase

35. Experiments were carried out using the apparatus below.

In which of the following conditions was oxygen produced most rapidly?Number of potato discs Condition of potato discs

A. 5 boiledB. 10 boiledC. 5 rawD. 10 raw

36. Which of the following graphs shows the effect of substrate concentration on enzyme activity? A. B.

C. D.

37. Which of the following can reduce the effect of a competitive inhibitor on enzymes?(1) increasing the substrate concentration(2) adding another non-competitive inhibitor(3) decreasing the temperature at which the reaction takes placeA. (1) onlyB. (1) and (2) onlyC. (1) and (3) onlyD. (1), (2) and (3)

rubber cap

oxygen

hydrogen peroxide solutionpotato disc

substrate concentration

enzy

me

activ

ity

enzy

me

activ

ity

substrate concentration

substrate concentration

enzy

me

activ

ity

substrate concentration

enzy

me

activ

ity

38. Which of the following statements about inhibitors is correct?

A. Cyanide and copper(II) ions are competitive inhibitors.

B. Competitive inhibitors alter the structure of enzymes.

C. Enzymatic activities cannot be restored by increasing substrate concentration in the presence of non-

competitive inhibitors.

D. All inhibitors have a similar shape with the substrate molecules.

Directions: Questions 39-41 refer to the following diagram, which shows a reaction involving enzyme X and s

ubstrate P. Molecules Q were then added. The figures in the diagram show their quantity in relative units.

39. If P and Q has similar affinity to enzyme X, which of the following would occur when 200 units of molecule

Q were added to the reaction involving enzyme X and substrate P?

A. The rate of reaction would increase by 20%.

B. The rate of reaction would decrease by 20%.

C. The enzyme would stop its activities.

D. The rate of reaction would not be affected.

40. If 2000 units of molecule R were added to the reaction instead of molecule Q, which of the following would

occur?

A. The rate of reaction will increase.

B. The rate of reaction would increase sharply.

C. Molecules R would block most of the enzymes.

D. The rate of reaction would not be affected.

41. If molecules Q had not been added to the reaction, what should be the quanitities of the enzyme and substrate

P after the reaction has been completed?

Enzyme X Substrate P

A. 0 unit 0 unit

B. 100 units 100units

C. 100 unit 0 unit

D. 0 unit 900 units

42. An experiment was carried out to investigate the effects of two metals on enzyme activities. An enzyme and its substrate were incubated at 40oC with various concentrations of either metal X or metal Y. The time taken for the complete breakdown of the substrate was measured. The results were recorded in the table below.

Concentration (ppm) Time needed to break down the substrate (seconds)

Metal X Metal Y

0 57 57

2 60 33

4 420 69

6 1500 339

(ppm = parts per million)Which of the following correctly describes the effects of high concentration of these metals on enzyme activity?

High concentration of metal X High concentration of metal YA. inhibited promotedB. inhibited inhibitedC. promoted inhibitedD. promoted promoted

43. The graph below shows the reaction rate of an enzyme without inhibition and that of the same enzyme in the presence of an inhibitor. Which curve represents the effect of a non-competitive inhibitor?

A. (1)B. (2)C. (3)D. (4)

44. In an investigation to determine the effect of temperature on the activity of an enzyme, the time for all the

substrate to disappear from a standard solution was recorded.

Which graph shows the results of this investigation?

Substrate concentration

(1)no inhibition

(2)

(3)(4)

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45. In the following graph, each of the curves P, Q and R represents an enzyme-controlled reaction in one of the

following situations:

- With the enzyme uninhibited

- With a non-competitive inhibitor added to the enzyme

- With a competitive inhibitor added to the enzyme

Which curve represents each situation?

Uninhibited enzyme competitive enzyme added non-competitive enzyme added

A. P R Q

B. P Q R

C. Q R P

D. R P Q

Directions: Questions 46 to 47 refer to the experiment below.

TEST 1: 1 g of freshly ground liver was placed in a test tube with 1 cm3 of hydrogen peroxide. A gas was formed.

The gas re-lit a glowing splint

TEST 2: 1 g of ground liver was boiled. When fresh hydrogen peroxide was added to the boiled liver, no gas was

formed.

TEST 3: Ground liver treated with strong acid produced results similar to those obtained in test 2.

TEST 4: Ground liver treated with strong alkali produced results similar to those obtained in test 2.

46. A hypothesis about enzyme activity in liver is being tested. The hypothesis is that the enzyme activity is

affected byA. acids, alkalis, boiling and hydrogen peroxide.B. acids, alkalis and hydrogen peroxide.C. acids, alkalis and boiling.D. grinding the liver.

47. Which of the following test tubes was the control for the experiment?A. the one containing boiled liver and hydrogen peroxideB. the one containing freshly ground liver and hydrogen peroxideC. the one containing liver treated with alkaliD. the one containing liver treated with acid

48. Which test(s) showed that the reaction was controlled by an enzyme?A. test 1 onlyB. test 1 and test 2 onlyC. test 2, test 3 and test 4 onlyD. test 1, test 2 , test 3 and test 4Directions: The following two questions refer to the diagrams below, which show the set-ups for investigating

the effectiveness of washing powders on stain removal.

(1)

protein stain

cloth

Non-biological powder at 25oC

(2)

lipid stain

cloth

Non-biological powder at 25oC

(3)

protein stain

cloth

Biological powder at 25oC

(4)

protein stain

cloth

Biological powder at 35oC

49. Which two set-ups are compared to show the effect of temperature on stain removal?

A (1) and (2) B (2) and (3)

C (2) and (4) D (3) and (4)

50. Which factor is being investigated by comparing (1) and (2)?

A temperature B type of washing powder

C type of cloth D type of stain

51. Which of the following is/are the advantage(s) of using enzymes in industrial processes?

(1) Can reduce the production of unwanted products

(2) Only small amount is required

(3) Can work well in low temperature

(4) Does not need extreme and expensive conditions such as very high temperature or pressure.

A. (1) and (2)

B. (1), (2) and (3)

C. (2), (4)

D. (1), (2) and (4)

52. How can enzymes help in manufacturing sofa?

A. Making it tougher by digesting fibre

B. Remove hairs from hides (牛皮)

C. Making the color of the sofa

D. Make it more spongy