Multiple-choice test
Chapter 5: Enzymes
Click on the correct answer to each question.
1 Which statement about enzymes is true?
A All enzymes are proteins.
B All enzymes have an optimum temperature of about 38 °C.
C Enzymes are denatured at low temperatures.
D Enzymes are killed at high temperatures.
2 Which statement is not true for all enzymes?
A Enzymes break down large molecules to small ones.
B Enzymes remain unchanged at the end of a reaction.
C Enzymes are affected by pH.
D Enzymes catalyse reactions.
3 Where are enzymes found?
A only in the digestive system
B in animals but not in plants
C in all living cells
D in plants but not in animals
4 Some catalase was added to some hydrogen peroxide. Bubbles
of oxygen were given off. After a while, the reaction stopped.
Why did the reaction stop?
A The catalase was all used up.
B The catalase was denatured by the reaction.
C The hydrogen peroxide was all broken down.
D The oxygen given off inhibited the catalase.
5 Which type of enzyme digests starch?
A catalase
B carbohydrase
C lipase
D protease
© Cambridge University Press 2014 IGCSE Biology Chapter 5: Enzymes Multiple-choice test 1
S 6 A student investigated the effect of temperature on the rate of
activity of a protease enzyme.
Which variable should she change, and which should she keep
constant?
Change Keep constant
A enzyme concentration substrate concentration
B substrate concentration temperature
C temperature pH
D pH enzyme concentration
7 Catalase catalyses a reaction in which hydrogen peroxide is
broken down to water and oxygen.
What are the substrate and product in this reaction?
Substrate Product
A catalase hydrogen peroxide
B hydrogen peroxide water and oxygen
C oxygen and water catalase
D water oxygen
8 What is an active site?
A a gland that secretes a particular enzyme
B a part of an enzyme molecule into which a substrate
molecules fits
C a part of the substrate to which an enzyme molecule attaches
D a place in the body where an enzyme works
9 Why does the rate of an enzyme-catalysed reaction increase as
temperature is raised from 0–40 °C?
A The enzyme and substrate molecules have more kinetic
energy, so they collide more frequently.
B The shape of the active site changes so that the substrate fits
into it better.
C Enzymes are denatured at low temperatures.
D The shape of the substrate changes at high temperatures.
10 Why does pH affect enzyme activity?
A Changes in pH affect the shape of the active site.
B Changes in pH affect the frequency of collisions between
enzyme and substrate.
C Changes in pH affect enzyme concentration.
D Changes in pH affect the enzyme’s optimum temperature.
© Cambridge University Press 2014 IGCSE Biology Chapter 5: Enzymes Multiple-choice test 2
