1. Grade 10 - Enzymes
Enzyme Action

2. Changing Reaction Rates
Certain factors help speed up reactions which normally would take a long time to proceed.
An example of this is when Hydrogen Peroxide breaks down to form water and oxygen:
2H2O H2O O2
When this reaction is heated, the reaction rate (amount of chemical change per unit time) increases!
The energy (e.g. Heat) required to make any chemical reaction proceed is called the ACTIVATION ENERGY
(Hydrogen Peroxide)
(Water)
(Oxygen)

3. Catalysts
Not only does heat (temperature) effect the reaction rate, but other chemicals also help speed the reactions up.
Manganese Dioxide is a chemical which helps the Hydrogen Peroxide reaction proceed faster.
A substance which increases the rate of reaction is called a CATALYST.
There are also biological (protein) catalysts and these are called ENZYMES!
Enzymes are protein molecules which occur naturally in all living cells.
Catalase is an enzyme found in liver cells which helps speed up the Hydrogen Peroxide reaction.

4. Properties of an Enzyme:
Biological Catalyst
Lowers the energy input/activation energy required for a chemical reaction to proceed.
Speeds up rate of reaction
Enzymes are proteins
Enzymes remain unchanged after a reaction and therefore can work again.
Enzymes are specific to a substrate of a reaction (Lock and Key).
Enzymes are reversible and can catalyse a reaction going both ways (Synthesis/Lysis)
Enzymes are denatured by:
Change in Temperature
Change in pH
Therefore have an optimum Temperature and pH, where it works most effectively. In Humans that is usually around 37˚C and a pH of 7.

5. Catalase experiments

6. Activation energy with/without Enzymes
(Substrates)
(Products)

7. ENZYME-SUBSTRATE COMPLEX
Specificty of Enzymes
Lock and Key Mechanism:
On Enzyme surface there is the active site which fits specifically with the substrate molecule it is suited to work on.
Active Site
Active Site unchanged, can now work on a new substrate.
SUBSTRATE
ENZYME-SUBSTRATE COMPLEX
PRODUCTS

8. Degradation of Complex Substrate
Degradation/lysis (breaking down) of complex substrate

9. Synthesis of Complex Product
Synthesis (building up) of complex product

10. Effect of Amylase Enzyme on starch (Degradation)
glucose
glucose
glucose
glucose
glucose
glucose
Amylase Enzyme
glucose
glucose
glucose
glucose
MALTOSE
glucose
Amylase Enzyme
glucose
glucose
glucose
glucose
glucose
Amylase Enzyme
glucose
glucose
glucose
glucose

11. Effect of phosphoraylase on Glucose-1-phosphorylase (Synthesis)
Glucose-1-Phosphate
How do you test for starch? (Iodine)… so wouldn’t this be a good test to see the effect of Phosphorylase
Phosphorylase Enzyme
Bond forming between two Glc molecules
Glucose-1-Phosphate
Phosphorylase Enzyme
Ect………….
STARCH molecule formed
Phosphorylase Enzyme

12. The equations for the previous reactions:
Effect of amylase (degradation)
Starch Maltose (simple sugar)
Effect of potato phosphorylase (synthesis)
Glucose-1-phosphate Starch
(Substrate)
(Products)
Amylase
(Substrate)
(Products)
Potato Phosphorylase

13. Effect of Temp/pH on Enzyme Activity
Optimum Temp/pH for enzyme activity!
Rate of Reaction/Enzyme Activity
Enzyme is becoming denatured (the active site is being physically altered (permanent damage)
Temp/pH (Arbitary units)

14. Digestion of starch by amylase

15. pH and Enzyme activity