1. Quick test What is the definition of a catalyst?
What type of molecule is an enzyme?
What is the active site?
What is the name of the substance that binds at the active site?
What is a synthesis reaction?
What does specificity mean in the context of enzymes?
What type of enzyme breaks down proteins?
Name one process in the body that relies on enzymes

2. Starter questions on enzymes
Starter questions on enzymes 
Enzymes _______ up the rate of chemical ________.
Enzymes are ________ because they only work on one substrate.
The substrate fits into the ________ site of the surface of the _______.
Enzymes can be re-used, so only _______ amounts are needed.
To which group of chemical compounds do enzymes belong? _________
Why is an enzyme specific for a particular substrate? _________________________________________
Why can an enzyme be used again and again? _________________________________________

3. Starter questions on enzymes
Starter questions on enzymes 
Enzymes speed up the rate of chemical reaction
Enzymes are specific because they only work on one substrate.
The substrate fits into the active site of the surface of the enzyme
Enzymes can be re-used, so only small amounts are needed.
To which group of chemical compounds do enzymes belong? Proteins
Why is an enzyme specific for a particular substrate? The active site of the enzyme is complementary to one type of substrate only.
Why can an enzyme be used again and again? They are catalysts which means that they allow the reaction to happen at a faster rate, without being used up or changed themselves.

4. Factors affecting enzyme action
Learning objectives
Describe and explain the effect of temperature and pH on the rate of enzyme catalysed reactions
Understand that denaturation results in a change to the active site.

5. Exam technique
DESCRIBE – what does it look like? Imagine someone can’t see the graph/table. Give enough detail so that they can picture exactly what the pattern is.
EXPLAIN – why does it look like that? Use scientific knowledge to account for the pattern described.

6. Describe how the rate of reaction of an enzyme reaction changes at different temperatures
(always include data)
Optimum temperature
Rate Of
Reaction
Temperature/oC

7. Describe
As the temperature increases the rate of reaction increases from 0oC to 40oC.
The optimum temperature (peak rate of reaction) is at 40oC.
As the temperature increases beyond 40oC, the rate of reaction decreases. (More rapidly than the increase in rate to 40oC).
The rate of reaction reaches 0 at 60oC

8. Explain why the rate of reaction of an enzyme reaction changes at different temperatures
Optimum temperature
Enzyme molecules
are denaturing
Molecules gain kinetic energy
Rate Of
Reaction
All enzyme molecules
are denatured
Temperature/oC

9. Explain why the rate of reaction of an enzyme reaction changes at different temperatures
0-40oC
An increase in temperature increases the kinetic energy of the enzyme and substrate molecules.
The molecules move about faster and result in an increase in collisions resulting in the formation of enzyme-substrate complexes.
Collisions are more frequent and energetic.
>40oC
High temperatures cause the amino acid chains to alter, which distorts the shape of the active site.
The substrate can no longer fit at the active site – it has been denatured.
The enzyme is no longer able to catalyse the reaction.
In humans the optimum temperature for enzymes is 37oC

10. Explain Optimum temperature Rate Of Reaction Temperature/oC
Enzyme molecules
are denaturing
Molecules gain kinetic energy
Rate Of
Reaction
All enzyme molecules
are denatured
Temperature/oC

11. Effects of pH on enzyme action

12. The activity of enzymes is also affected by pH
Enzymes work best at an optimum pH.
The pH change alters the forces that hold the amino acid chains in place at the active site.
Outside of its pH range the enzyme is denatured.
Optimum pH
pepsin
amylase
Rate Of
Reaction pH

13. Denaturing
A change to the 3D shape of the active site of the enzyme caused by high temperatures or a change in pH.
The enzyme no longer works as a catalyst.
The damage can sometimes be irreversible
The enzyme has NOT died….it was never alive!

14. Substrate
Substrate
Complementary
active site
Active site
changed
Enzyme
Enzyme is denatured

15. Describe and explain the effect of temperature on the rate of the enzyme controlled reaction
Include these key words in your answer….
Denatured Optimum temperature
Active site Kinetic energy
Substrate Reaction
Collision Enzyme-substrate complex
Frequent Energetic
Amino acid

16. Examples of enzymes in your body…
Use
Protease (in the stomach)
Breaking down proteins
Amylase (in the mouth)
Breaking down carbohydrates
Lipase (in the intestines)
Breaking down fats
Catalase (in the liver)
Breaks down hydrogen peroxide

17. respiration rate shape chain amino acid reactant amylase specificity
Write a scientific clue/definition for the words below. There can only be 1
correct ‘splat’ to your question.
respiration
rate
shape
chain
amino acid
reactant
amylase
specificity
protease
lock & key
biological
enzyme
product
protein
reaction
synthesis
catalyst
active site
substrate

18. Practical next lesson……
To investigate the effects of temperature on the activity of pectinase in forming apple juice.
(Pectinase degrades pectin in the apples so that juice is produced more readily)
Plan a practical
Include a step by step method
Identify the independent, dependent and control variables
Safety points