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1 Pectinase is an enzyme that is used in the production of apple juice.

A student investigated how pH affected the volume of apple juice produced when

using pectinase. The student chopped an apple into small pieces.

The pieces of apple were put into solutions with different pH

values. Pectinase was added to each solution.

After two hours the mixture was filtered and the volume of apple juice obtained was

recorded. The table shows the results.

volume of apple
pH
juice obtained / cm3
1.0 23.2
2.0 24.2
3.0 23.5
4.0 25.7
5.0 27.6
6.0 27.4
7.0 24.0
8.0 22.0

State one factor, other than pH, that would affect the activity of pectinase.

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[Total: 1]
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2 Pectinase is an enzyme.

The box on the left shows the beginning of a

sentence. The boxes on the right show some

endings of sentences.

Draw three lines from the word ‘Enzymes’ to make three correct sentences.

are living organisms.

are proteins.

Enzymes can only be used once.

have a complementary shape to their

substrate.

increase the rate of chemical reactions.

in the stomach are most active at pH 8.

[3]

[Total: 3]
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3 Biological washing powders contain enzymes that break down food stains.

Some students compared how effective biological and non-biological washing

powders are at removing stains at temperatures between 10 °C and 60 °C.

•Pieces of stained cloth were washed using two different washing powders.

•The degree of stain removal was measured by using a light meter to record the
percentage of light reflected from the cloth.

•A light meter gave a value of 100% when the cloth was completely clean.

•Any stain left on the cloth reduced the percentage of light reflected.

The results of the students’ investigation are shown in the graph.

The students suggested that the enzymes in the biological washing powder were
denatured at high temperatures.

Explain why enzyme molecules do not function when they are denatured.

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[Total: 2]

4 Amino acids are transported in plants.

State the name of the group of molecules that are made of proteins and act as
catalysts.

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[Total: 1]
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5 A student investigated the rate of oxygen uptake during aerobic respiration in

woodlice. Woodlice are arthropods.

The diagram shows the apparatus the student used. Soda lime absorbs carbon
dioxide.

When the tap is closed air cannot move into or out of the apparatus. The coloured
liquid moves when the tap is closed.

The table shows the results of this investigation.

position of the coloured

time / minutes
liquid on the ruler
scale / cm
0 1.0
2 2.1
4 3.1
6 4.2
8 5.5
10 5.9
12 7.5

Suggest why it is important that the temperature of the apparatus did not exceed 40
°C.

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[Total: 2]
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6 Catalase is an enzyme that catalyses the breakdown of hydrogen peroxide into water
and oxygen.

The effect of temperature on catalase activity was

investigated. The results are shown in the graph.

State the temperature at which catalase is most active in the graph.

........................... °C [1]

[Total: 1]
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7 The graph shows how the rate of reaction of a digestive enzyme changes with pH.

State one factor other than pH that will affect enzyme activity.

................................................................................................................................... [1]

[Total: 1]
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8 The graph shows how the rate of reaction of a digestive enzyme changes with pH.

Describe the effect of the increase in pH on the rate of reaction shown in the graph.

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[Total: 2]
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9 Catalase is an enzyme that catalyses the breakdown of hydrogen peroxide into water
and oxygen.

The effect of temperature on catalase activity was

investigated. The results are shown in the graph.

Explain why there is no enzyme activity at 60°C.

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[Total: 1]
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10 Catalase is an enzyme that catalyses the breakdown of hydrogen peroxide into water
and oxygen.

The effect of temperature on catalase activity was

investigated. The results are shown in the graph.

State one factor other than temperature that affects enzyme activity.

................................................................................................................................... [1]

[Total: 1]
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11 The cut surface of an apple usually turns brown when exposed to air. This is caused
by enzymes.

Three slices of apple were given different treatments and were then exposed to air for

30 minutes. The table shows the treatments and appearance of the apple slices.

appearance of
appearance of the
apple slice pH temperature / °C the apple slice
apple slice at 0
after 30
minutes
minutes
A 6 20 white brown
B 2 20 white white
C 6 4 white white

Suggest why slice B and slice C did not turn brown after 30 minutes.

slice B
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slice C
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[Total: 2]

12 A factory uses biotechnology to process apples.

Some of the apple juice is mixed with yeast and used to make

ethanol. The yeast uses enzymes to produce ethanol.

Define the term enzyme.

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[Total: 2]

13 The digestive systems of young mammals are not fully developed.

Enzymes such as amylase, maltase and protease are often added to baby food to aid
chemical digestion.
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(a) (i) Suggest why the temperature of baby food must be controlled when the
enzymes are added.

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(ii) State one other condition that must also be controlled to optimise enzyme
activity.

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[Total: 3]

14 Glycogen is a storage carbohydrate in animals. Glycogen is made from glucose.

State the type of biological molecule that catalyses reactions such as the conversion
of glycogen to glucose.

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[Total: 1]
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15 The reactions of chemical digestion are catalysed by enzymes.

The diagram shows the stages of an enzyme-catalysed reaction.

State the names of A to D in the diagram.

A ........................................................................................................................................
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B ........................................................................................................................................
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C ........................................................................................................................................
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D....................................................................................................................................................[4]

[Total: 4]
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16 This question is about enzymes.

Choose words from the list to complete the

sentences. Each word may be used once, more

than once, or not at all.

amino acids amylase bacteria biological

fatty acids glucose humidity lipase

living protease salivary temperature

All enzymes are proteins. Proteins are made of ............................................... .

An enzyme acts as a.......................................catalyst.

In order to work rapidly, enzymes need the correct................................and pH.

An example of an enzyme that works in the acidic conditions in the stomach is

............................................... .

Acidic conditions will kill many of the...................................present in food.

Salivary.........................................stops working in acidic conditions.

Fats are broken down by ............................................... .

[7]

[Total: 7]
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17 A student investigated the activity of the digestive enzyme pepsin.

The diagram shows the apparatus used in the investigation.

The appearance of the four test-tubes was recorded at 0 and 5

minutes. The protein in the egg white solution gives the solution a

cloudy appearance.

The cloudy appearance clears when the protein in the egg white solution

breaks down. The table shows the results.

test-tube contents appearance at 0 mins appearance after 5

mins
1 egg white solution, cloudy less cloudy
pepsin
egg white solution,
2 cloudy clear
pepsin, hydrochloric
acid
egg white solution,
3 cloudy cloudy
boiled pepsin,
hydrochloric acid
egg white solution,
4 cloudy cloudy
hydrochloric acid

Explain the purpose of test-tube 4.

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[Total: 2]
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18 A student investigated the activity of the digestive enzyme pepsin.

The diagram shows the apparatus used in the investigation.

The appearance of the four test-tubes was recorded at 0 and 5

minutes. The protein in the egg white solution gives the solution a

cloudy appearance.

The cloudy appearance clears when the protein in the egg white solution

breaks down. The table shows the results.

appearance appearance
test-tube contents
at 0 mins after 5
mins

egg white solution,

1 cloudy less cloudy
pepsin

egg white
2 solution, pepsin, cloudy clear
hydrochloric acid

egg white solution,

3 boiled pepsin, cloudy cloudy
hydrochloric acid

egg white solution,

4 cloudy cloudy
hydrochloric acid

Explain the results shown for test-tubes 1, 2 and 3 in the table.

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[Total: 5]

19 What is the optimum pH for stomach enzymes?

A pH B pH C pH D pH
2 7 9 12
[1]

[Total: 1]

20 During digestion, what is the function of an enzyme?

A to break down fats into droplets

B to break down food into small pieces
C to break down large molecules into small
molecules
D to kill bacteria in food
[1]

[Total: 1]
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21 Four test-tubes were set up as shown in the table.

In which test-tube would starch be broken down the fastest?

2 cm3 starch
1 cm3 of 1 cm3 of temperature
suspension
amylase boiled / °C
added
added amylase
added
A ✓ ✓ ✗ 5

B ✓ ✓ ✗ 35

C ✓ ✗ ✓ 5

D ✓ ✗ ✓ 35

key

✓ = present

✗ = absent

[1]

[Total: 1]

22 Which statement about enzymes is correct?

A Enzymes become part of the product.

B Lowering the pH always slows down the reaction rate.
C Raising the temperature always increases the reaction rate.
D The specificity of an enzyme depends on the shape of its
active site.
[1]

[Total: 1]

23 Why does excessive heat decrease enzyme activity?

A It changes the shape of the active site.

B It changes the shape of the substrate and product molecules.

C It increases the force of collisions between substrate and product

molecules.
D It increases the kinetic energy of the substrate molecules.
[1]

[Total: 1]
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24 The diagram shows an enzyme with its substrate and product molecules.

Q
P

Which form an enzyme-substrate complex?

A P and B Q and C R and D S and

Q R S P
[1]

[Total: 1]

25 Which statement about enzymes is correct?

A Enzymes are carbohydrates.

B Enzymes are catalysts.
C Enzymes are living organisms.
D Enzymes are the same shape as the
substrate.
[1]

[Total: 1]
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26 The diagram represents an enzyme-controlled reaction.

What represents an enzyme?

A D

[1]

[Total: 1]

27 The diagrams show an experiment on enzyme activity.

The test-tubes contain hydrogen peroxide and the enzyme

catalase. In which test-tube is the enzyme inactive?

A B C D

mixture mixture mixture

of of boiled of
catalase catalase catalase
and and and
hydroge hydroge boiled
n n hydroge
peroxide peroxide n
at 4 C at 37 at 37 at 37
C C peroxide C
[1]

[Total: 1]
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28 Chemical digestion is the breakdown of large, insoluble molecules into smaller,

soluble molecules. Digestive enzymes such as lipase are used in this process.

Define the term enzyme.

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[Total: 2]

29 The first diagram represents a chemical reaction.

reactants product

Which diagram, below, represents the enzyme for this reaction?

A B C D

[1]

[Total: 1]

30 Name one factor, other than pH, which can change the rate of enzyme activity.

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[Total: 1]
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31 The digestive system produces enzymes.

Define the term enzyme.

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[Total: 2]

32 Complete the following paragraph about enzymes. Choose words from this list.

Use each word only once or not at all.

activators catalysts enzymes

protein reactions unusual

All enzymes are made of.............................................molecules. They control the

metabolic...............................................in living organisms. The enzymes act as

.............................................as they speed up processes but are not permanently

changed.

[3]

[Total: 3]
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33 The graph below shows how the reaction rates of two different enzymes, L and M,
vary when the pH changes.

Use the graph to state the pH at which each of these enzymes work the fastest.

pH for enzyme L: ...........................

pH for enzyme M:..........................[2]

[Total: 2]

34 In an investigation to measure the effect of pH on enzyme activity, a protease

enzyme was mixed with solutions of different pH values. The mixtures were placed in
holes cut in the centre of dishes of gelatin.

Gelatin is a protein which can be stained with a coloured dye. When the protease
digests the gelatin a colourless zone forms.

The diagram below shows a dish at the start of the experiment.

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stained gelatin (a protein)

hole containing mixture

of solution and

protease dish

at the start

The diagram below shows the dishes after a period of 24 hours.

pH 2

gelatin colourless zone

pH 4 pH 6 pH 8 pH 10

after 24 hours

(a) (i) Using the diagram that shows the dishes after a period of 24 hours, state
the optimum

(best) pH for the activity of this protease ..................

[1]

(ii) Suggest the region of the alimentary canal in which this protease carries out
its function.

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(iii) Complete the equation to explain how the protease caused the
colourless zones to appear.

[2]
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(b) The experiment was carried out at 20°C.

Suggest what would happen if the experiment was carried out at 30°C.

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[Total: 5]

35 Saliva contains an enzyme that digests starch.

A group of students used saliva to investigate the digestion of starch at different

pH values. Their results are shown in the graph below.

(a) (i) At which pH does the enzyme in saliva work the fastest?

....................................................[1]

(ii) How long does it take for the starch to be digested at pH 6?

....................................................... min
[1]
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(iii) The stomach produces hydrochloric acid.

Use the graph to suggest why the enzyme found in saliva does not work
inside the stomach.

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[Total: 4]

36 Researchers in Michigan investigated the rate of photosynthesis in leaves of big-tooth

aspen trees,
Populusgrandidentata, by placing some of the growing leaves inside transparent boxes.

The researchers measured the uptake of carbon dioxide by the leaves over a range of
temperatures from 10–40 °C. They carried out their measurements at two different
concentrations of carbon dioxide:

H – 325 ppm carbon dioxide which is close to the concentration in the

atmosphere;

J – 1935 ppm carbon dioxide which is a very high concentration.

The results are shown in the graph below.

30

25 J

20
uptake of
15
carbon dioxide
/ mg m–2 min–1
10
H
5

0
0 5 10 15 25 35 40
20
30
temperature / °C

(a) Explain why the rate of photosynthesis in the leaves in batch J:

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(i) increases with an increase in temperature from 15 °C to 35 °C

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(ii) decreases at temperatures above 35 °C.

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[Total: 4]