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Biology questions, chapter 5
Nama / NameKelas / ClassTarikh / Date

Metabolism and Enzymes

45 marks. Use Practice to check each answer as you go, or Exam to answer everything against the clock first.

Section A: objective questions

12 marks
Choose the best answer for each question.
1

Question 1

What is metabolism?
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B
Metabolism is all the chemical reactions in a living organism, including the conversion of food to ATP and the formation of carbohydrate, protein, lipid and nucleic acid.
For the teacher: Remembering, low difficulty, standard 5.1.1
Textbook p. 86
2

Question 2

Which process is an example of anabolism?
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D
Anabolism builds complex molecules from simple ones and uses energy. Glucose is made from carbon dioxide and water in photosynthesis. The other three are catabolic.
For the teacher: Understanding, low difficulty, standard 5.1.2
Textbook p. 86
3

Question 3

Which enzyme catalyses the hydrolysis of lactose?
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A
Enzymes are named by adding -ase to the substrate: lactose gives lactase.
For the teacher: Applying, low difficulty, standard 5.2.3
Textbook p. 87
4

Question 4

Which enzyme does NOT follow the naming system of adding -ase to the substrate?
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C
Pepsin, trypsin and renin were named before the system was introduced and kept their names.
For the teacher: Remembering, low difficulty, standard 5.2.3
Textbook p. 87
5

Question 5

The substrate binds with an enzyme at a specific site. What is this site called?
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B
The substrate binds at the active site to form an enzyme-substrate complex.
For the teacher: Remembering, low difficulty, standard 5.2.1
Textbook p. 86
6

Question 6

Which sequence shows the production of an extracellular enzyme?
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D
The protein is made at the ribosome, passes through the rough ER in transport vesicles to the Golgi apparatus, then leaves in secretory vesicles through the plasma membrane.
For the teacher: Understanding, medium difficulty, standard 5.2.5
Textbook p. 88
7

Question 7

Which enzyme is an intracellular enzyme?
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A
Hexokinase works inside the cell that makes it. The other three are secreted out of the cell.
For the teacher: Understanding, low difficulty, standard 5.2.5
Textbook p. 88
8

Question 8

In the lock and key hypothesis, what does the key represent?
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C
The enzyme is the lock (with the active site) and the substrate is the key that fits it.
For the teacher: Remembering, low difficulty, standard 5.2.6
Textbook p. 89
9

Question 9

Diagram 1 shows the energy changes of a reaction with and without an enzyme. What does the graph show?
Energy graph with two curves: the reaction with enzyme has a lower peak
Diagram 1
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B
The curve with enzyme has a lower peak, so less activation energy is needed. Reactants and products are at the same levels in both curves.
For the teacher: Analysing, medium difficulty, standard 5.2.7
Textbook p. 89
10

Question 10

Why does enzyme activity stop at about 60 °C?
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D
At high temperature the bonds in the enzyme break, the three-dimensional shape is lost and the substrate no longer fits the active site.
For the teacher: Understanding, low difficulty, standard 5.2.8
Textbook p. 90
11

Question 11

Diagram 2 shows the effect of pH on three enzymes. What is the optimum pH of pepsin?
Graph of rate of reaction against pH for pepsin, salivary amylase and trypsin
Diagram 2
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A
The pepsin curve peaks at about pH 2, an acidic condition like the stomach. 6.8 is amylase and 8.5 is trypsin.
For the teacher: Applying, medium difficulty, standard 5.2.8
Textbook p. 90
12

Question 12

The rate of an enzyme reaction stops increasing when more substrate is added, although the enzyme concentration is fixed. What is the reason?
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C
At the maximum rate every active site is saturated with substrate. Only more enzyme can raise the rate further.
For the teacher: Analysing, high difficulty, standard 5.2.8
Textbook p. 91

Section B: structured questions

33 marks
Answer all questions.
13

Question 13

Trypsin is an enzyme made by pancreatic cells and secreted into the duodenum.
[2 marks] (a)Is trypsin an intracellular or extracellular enzyme? Give a reason.
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[1 mark] (b)Which organelle makes the protein of the enzyme?
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[2 marks] (c)State the role of the Golgi apparatus in the production of the enzyme.
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For the teacher: Understanding, low difficulty, standard 5.2.5
Textbook p. 88
14

Question 14

A student studied the effect of temperature on amylase. Starch and amylase were mixed at each temperature and tested with iodine at regular intervals. Table 1 shows the time for starch to disappear.
Temperature (°C)2030405060
Time for starch hydrolysis (minutes)12845No hydrolysis
Table 1
[1 mark] (a)State the manipulated variable.
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[2 marks] (b)Calculate the rate of reaction at 20 °C. Rate = 1 ÷ time.
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1 ÷ 12 = 0.0833.
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[2 marks] (c)At which of the temperatures tested is the enzyme most active? Give a reason.
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[2 marks] (d)Explain why there is no hydrolysis at 60 °C.
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For the teacher: Applying, medium difficulty, standard 5.2.9
Textbook p. 92
15

Question 15

Three test tubes each contain albumen suspension (cloudy) and pepsin. Hydrochloric acid is added to P, distilled water to Q and sodium hydroxide to R. All are kept in a 37 °C water bath for 20 minutes. Only tube P becomes clear.
[1 mark] (a)Why are the tubes kept in a water bath at 37 °C?
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[2 marks] (b)Explain why tube P becomes clear.
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[2 marks] (c)Explain why tubes Q and R stay cloudy.
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[1 mark] (d)State the responding variable.
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For the teacher: Analysing, medium difficulty, standard 5.2.9
Textbook p. 94
16

Question 16

Explain the mechanism of enzyme action.
[1 mark] (a)Name the hypothesis used to explain how enzymes act.
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[2 marks] (b)In this hypothesis, what represents the structure of the enzyme and the structure of the substrate?
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[2 marks] (c)Explain why only certain substrates can combine with an enzyme.
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For the teacher: Understanding, low difficulty, standard 5.2.6
Textbook p. 89
17

Question 17

Enzymes are used in food preparation and industry.
[2 marks] (a)Some chefs wrap meat in papaya leaves before cooking. Explain the purpose.
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[2 marks] (b)A peeled apple that has been boiled does not turn brown. Explain why.
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[2 marks] (c)Give two advantages of using an immobilised enzyme in industry.
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For the teacher: Evaluating, high difficulty, standard 5.3.1
Textbook p. 97
18

Question 18

A cell carries out two types of metabolism.
[2 marks] (a)Define catabolism and give one example.
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[2 marks] (b)Define anabolism and give one example.
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For the teacher: Remembering, low difficulty, standard 5.1.2
Textbook p. 86