MCQ-3 Biology – CIE IGCSE Level: Enzymes

Question 1 of 20

1. Question

1 point(s)

The diagram shows the effect of an enzyme working in the human digestive system.

What would reduce the rate of production of amino acids?

removing the amino acids as they are formed
increasing the amount of protein
raising the temperature to 40 °C
raising the pH to 7.5

Question 2 of 20

2. Question

1 point(s)

What controls the speed of chemical reactions in all living cells?

enzymes
hormones
ions
vitamins

Question 3 of 20

3. Question

1 point(s)

The graph shows the effect of temperature on an enzyme-controlled reaction.

Which statement describes the effect of temperature on this reaction?

As the temperature increases to 25°C the reaction speeds up
Between 10°C and 20°C the enzyme stops working
Between 35°C and 45°C the enzyme stops working
The optimum temperature for this reaction is 40°C

Question 4 of 20

4. Question

1 point(s)

The graph shows the effect of pH on the activity of a human digestive enzyme.

What is the enzyme?

amylase
maltase
pepsin
trypsin

Question 5 of 20

5. Question

1 point(s)

The diagram shows a protease molecule catalysing the break down of a protein molecule.

What are the parts labelled P, Q, R and S?

	enzyme	product	substrate	active site
A	P	Q	R	S
B	R	S	P	Q
C	S	P	Q	R
D	S	R	Q	P

Option A
Option B
Option C
Option D

Question 6 of 20

6. Question

1 point(s)

Which statement about enzymes is correct?

Enzymes become part of the product
Lowering the pH always slows down the reaction rate
Raising the temperature always increases the reaction rate
The specificity of an enzyme depends on the shape of its active site

Question 7 of 20

7. Question

1 point(s)

Which enzyme is used to produce clear apple juice?

amylase
lipase
pectinase
protease

Question 8 of 20

8. Question

1 point(s)

Where in the alimentary canal is the enzyme trypsin found and what are the products of the reaction it catalyses?

	where trypsin is found	products
A	duodenum	amino acids
B	duodenum	fatty acids
C	ileum	proteins
D	stomach	amino acids

Option A
Option B
Option C
Option D

Question 9 of 20

9. Question

1 point(s)

Why does excessive heat decrease enzyme activity?

It changes the shape of the active site
It changes the shape of the substrate and product molecules
It increases the force of collisions between substrate and product molecules
It increases the kinetic energy of the substrate molecules

Question 10 of 20

10. Question

1 point(s)

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 suspension added	1 cm³ of amylase added	1 cm³ of boiled amylase added	temperature /°C
A	✓	✓	x	5
B	✓	✓	x	35
C	✓	x	✓	5
D	✓	x	✓	35

key
✓ = present
x = absent

Option A
Option B
Option C
Option D

Question 11 of 20

11. Question

1 point(s)

The diagram shows an enzyme with its substrate and product molecules.

Which form an enzyme-substrate complex?

P and Q
Q and R
R and S
S and P

Question 12 of 20

12. Question

1 point(s)

Which substrate, enzyme and product are correctly named?

	substrate	enzyme	product
A	amino acids	trypsin	protein
B	amylase	maltose	glucose
C	lipase	lipid	fatty acids and glycerol
D	maltose	maltase	glucose

Option A
Option B
Option C
Option D

Question 13 of 20

13. Question

1 point(s)

The apparatus shown is used for an experiment on starch digestion.
Which test-tube contains the most sugar after 20 minutes?

Option A
Option B
Option C
Option D

Question 14 of 20

14. Question

1 point(s)

A student wrote some notes about enzymes.
She wrote:
‘The ……1…… of the 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?

	1	2	3
A	active site	complementary	enzyme-substrate
B	active site	similar	enzyme-product
C	shape	complementary	enzyme-product
D	shape	similar	enzyme-substrate

Option A
Option B
Option C
Option D

Question 15 of 20

15. Question

1 point(s)

The graph shows the effect of temperature on the action of an enzyme.

Why does the rate of reaction change when the temperature is increased from 20 °C to 30 °C?

	more kinetic energy of particles	more frequent collisions of particles
A	✓	✓
B	x	✓
C	✓	x
D	x	x

Option A
Option B
Option C
Option D

Question 16 of 20

16. Question

1 point(s)

Which row shows an enzyme with the correct site of production and products?

	enzyme	enzyme produced by	product(s) of digestion
A	amylase	salivary glands	amino acids
B	amylase	stomach	sugar
C	protease	salivary glands	sugar
D	protease	stomach	amino acids

Option A
Option B
Option C
Option D

Question 17 of 20

17. Question

1 point(s)

The graph shows how an enzyme-controlled reaction is affected by temperature.

Which statement explains the change in activity between X and Y?

There are more effective collisions
There is a change in the enzyme shape
There is more substrate present
The kinetic energy of the molecules has increased

Question 18 of 20

18. Question

1 point(s)

What is the correct definition of the term enzyme?

carbohydrates that act as biological catalysts
carbohydrates that act as substrates
proteins that act as biological catalysts
proteins that act as substrates

Question 19 of 20

19. Question

1 point(s)

Enzyme X digests protein in the stomach.
Four test-tubes were set up, each contained the same amounts of protein and enzyme X. The test-tubes are kept at different levels of pH and temperature, as shown in the table.
In which test-tube will protein digestion be quickest?

	pH	temperature / °C
A	2	20
B	2	35
C	7	20
D	7	35

Option A
Option B
Option C
Option D

Question 20 of 20

20. Question

1 point(s)

The activity of lipase is measured in four parts of the gut.
Which part has the most lipase activity?

colon
duodenum
oesophagus
stomach

Pos.	Name	Entered on	Points	Result
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Biology – Cambridge IGCSE: Enzymes

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MCQ-3: Enzymes

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