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Introduction to Enzymes
IGCSE Combined Science
Learning Outcomes
• Everyone should
-explain why enzymes are necessary for life
-state that enzymes are made of protein
• Most people will
-understand that an enzyme is a biological
catalyst
• Some people might
-be able to write out word equations for enzyme
reactions
What is a chemical reaction?
• It is when a substance reacts and changes in some way
‘Living’ reactions
Reactions that happen inside an organism are part of
processes called metabolism. For example:
Respiration
Digestion
Growth
Germination
Photosynthesis
Behold Hina’s Magical Pineapple
What affect has it had on the jelly?
Why do you think this has happened?
Important?
Almost all chemical reactions in an organism are controlled by enzymes.
Without enzymes these reactions
would go too slowly for life to exist.
Most processes in an organism consist of many reactions in sequence.
Each one is catalysed by a specific enzyme- one enzyme for one
reaction.
Some key words to listen
out for:
Catalyst
Substrate
Product
Enzyme
Metabolism
Active site
Specific
Enzymes
 Enzymes (and catalysts) take part in a reaction
but are unchanged at the end of it.
 They can be used over and over again but are
not used up in the reaction.
Describing reactions
Catalase
Hydrogen peroxide
Substrate
The molecule that an
enzyme works on
water
Enzyme
+ oxygen
Product
The molecule that is
produced
Now you try!
• Try the practice exercise on your handout
• If you finish quickly try the extension!
Can you?
-explain why enzymes are necessary for life?
-state what enzymes are made of?
-understand why an enzyme is a biological catalyst?
-write out a word equation for an enzyme reaction?