Home › IGCSE Biology › Practice › EnzymesCambridge IGCSE · Biology 0610
IGCSE Biology: Enzymes — Practice Questions & Answers
Understand enzymes as biological catalysts, the lock and key model, and how temperature and pH affect their activity.
638 practice questions available for this topic — here are 10 with full answers and explanations.
Start an interactive quiz on Enzymes →
Practice questions with answers
1
Multiple choice · Easy
What is an enzyme?
A biological catalyst made of protein
A type of carbohydrate that stores energy
A lipid that forms cell membranes
A mineral ion needed for respiration
Tap an answer to check it.
Why Enzymes are biological catalysts that speed up reactions and are made of protein.
2
Multiple choice · Easy
What name is given to the substance an enzyme acts on?
Substrate
Product
Catalyst
Cofactor
Tap an answer to check it.
Why The substrate is the molecule that an enzyme binds to and converts into products.
3
Multiple choice · Easy
The region of an enzyme where the substrate binds is called the
active site
binding chain
reaction core
product site
Tap an answer to check it.
Why The active site is the specific region of the enzyme where the substrate fits and reacts.
4
Multiple choice · Easy
Enzymes are described as catalysts because they
speed up reactions without being used up
are destroyed during the reaction
provide energy for the reaction
change the products that are formed
Tap an answer to check it.
Why A catalyst speeds up a chemical reaction without being changed or used up itself.
5
Multiple choice · Easy
Which chemical group are enzymes made from?
Proteins
Carbohydrates
Lipids
Nucleic acids
Tap an answer to check it.
Why All enzymes are proteins, made of chains of amino acids folded into a specific shape.
6
Multiple choice · Easy
What model is used to describe how an enzyme and its substrate fit together?
Lock-and-key model
Fluid mosaic model
Bohr model
Sliding filament model
Tap an answer to check it.
Why The lock-and-key model describes how a substrate fits the enzyme active site like a key fits a lock.
7
Multiple choice · Easy
What happens to an enzyme when it is denatured?
Its active site changes shape
It speeds up the reaction
It becomes a substrate
It turns into a carbohydrate
Tap an answer to check it.
Why Denaturation permanently changes the shape of the active site so the substrate no longer fits.
8
Multiple choice · Easy
Which factor below affects the rate of an enzyme-controlled reaction?
Temperature
Colour of the container
Mass of the test tube
Day of the week
Tap an answer to check it.
Why Temperature is one of the main factors affecting enzyme activity, along with pH and concentration.
9
Multiple choice · Medium
Why can one type of enzyme usually catalyse only one type of reaction?
Only a substrate with a complementary shape fits the active site
Each enzyme can only work once
Enzymes choose reactions at random
All substrates have the same shape
Tap an answer to check it.
Why Enzyme specificity arises because only a complementary substrate fits the shape of the active site.
10
Multiple choice · Medium
As temperature rises from 10 degrees C to 37 degrees C, the rate of an enzyme reaction increases. This is mainly because
molecules move faster and collide more often
the enzyme becomes denatured
the active site changes shape permanently
the substrate stops moving
Tap an answer to check it.
Why Higher temperature increases kinetic energy, so enzymes and substrates collide more often and successfully.
Key terms in Enzymes
Enzyme: A protein that acts as a biological catalyst, speeding up a specific chemical reaction in a living organism without being used up.
Biological catalyst: A substance made by living cells that increases the rate of a metabolic reaction without being changed or used up; enzymes are biological catalysts.
Catalyst: A substance that increases the rate of a chemical reaction without itself being changed or used up by the reaction.
Protein (enzyme structure): The class of molecule from which all enzymes are made; enzymes are proteins whose folded shape gives them their function.
Metabolic reaction: Any chemical reaction that takes place inside the cells of a living organism, the great majority of which are controlled by enzymes.
Metabolism: The sum of all the chemical reactions taking place in an organism, all of which are catalysed by enzymes.
Substrate: The molecule (or molecules) on which an enzyme acts and which is changed into product during the reaction.
Product: The new molecule (or molecules) formed when an enzyme has acted on its substrate.
See the full study notes and flashcards for this topic.
Practise other IGCSE Biology topics