1. Enzymes Enzymes are proteins that act as biological catalysts
They lower the activation energy of a specific chemical reaction
Lowering the activation energy has a profound effect on how rapidly the reaction is completed

2. Enzymes
Lower the activation energy of a reaction 2

3. Enzymes Lower Activation Energy

4. What are enzymes? Enzymes are typically proteins Enzymes are specific
Enzymes act as catalysts to speed up the rate of reaction of a biological process
Enzymes are not used up by the reaction they catalyse
Enzymes were discovered by a German chemist called Eduard Buchner near the end of the nineteenth century. He discovered enzymes while trying to extract yeast fluid for medicinal use when he noticed that the sugar was continually being converted into alcohol. Even though Louis Pasteur had shown this about twenty years before Eduard Buchner, Louis Pasteur had said that it was the yeast itself that made the conversion.Eduard Buchner said that it was not the yeast but the ‘juice’ inside them. The word enzyme was used for the active ingredient in the yeast juice. Enzyme literally means ‘in yeast’ ( ‘en’ = in, ‘zyme’ = yeast) and all enzymes are used as organic catalysts to speed up chemical reactions in organisms.Without enzymes reactions in cells would be so slow that they would virtually not take place.

5. Enzymes are essential to all forms of life…

6. Enzymes: Vocabulary Check
Catalyst: A substance that speeds up a chemical reaction without itself being changed
Enzyme: A biological catalyst that is usually a protein
Substrate: The reactant(s) upon which an enzyme has its action
Product: A substance that results from a chemical reaction

7. Enzyme-Substrate Interaction

9. Factors affecting Enzymes
Substrate concentration
Enzyme availability pH
Temperature
Inhibitors

10. Factors which affect enzyme activity 1: Temperature
From: GCSE Bitesize:

11. The effect of temperature
Temperature / °C
Enzyme activity 10 20 30 40 50
Q10
Denaturation

12. The effect of temperature
For most enzymes the optimum temperature is about 30°C
Many are a lot lower. For example, cold water fish can die at 30°C since many of their enzymes denature
A few bacteria have enzymes that can withstand very high temperatures up to 100°C
Most enzymes are fully denatured at 70°C

13. Factors which affect enzyme activity 2: pH
From: GCSE Bitesize:

14. The effect of pH Optimum pH values Enzyme activity Trypsin Pepsin pH 13 5 7 9 11
© 2007 Paul Billiet ODWS

15. The effect of pH Extreme pH levels will produce denaturation
The structure of the enzyme is changed
The active site is distorted and the substrate molecules will no longer fit in it
At pH values slightly different from the enzyme’s optimum value, small changes in the charges of the enzyme and its substrate molecules will occur
This change in ionisation will affect the binding of the substrate with the active site due to shape change.

16. Factors which affect enzyme activity 3: Substrate and enzyme concentration
From:
August 26th 2012

17. Complete this sentence…
The _____________ (more/less) enzyme, the faster the product is made.

18. Substrate concentration: Enzymic reactions
Reaction velocity
Substrate concentration
Vmax
Faster reaction but it reaches a saturation point when all the enzyme molecules are occupied.
If you alter the concentration of the enzyme then Vmax will change too.

19. Enzyme action can be blocked by:
1. Inhibition (many drugs work through enzyme inhibition) 2. Denaturation

20. Enzyme Inhibition

21. Denaturation
Denaturation is a change in the shape of an enzyme which prevents it from fulfilling its function. Enzymes (and other proteins) can be denatured by heat, pH changes, or certain chemicals NB: Denaturation is not the same as ‘killing’ – proteins and enzymes are not living things, so can’t be killed!

22. What does ‘enzyme denaturation’ mean?