Enzymes are proteins that function as biological catalysts to lower the activation energy of chemical reactions. They are specific and only act on particular substrates to produce products. The active site of the enzyme binds precisely to the substrate like a lock and key to form an enzyme-substrate complex from which products are released. Enzyme activity is optimized at particular temperatures and pH levels and can be denatured by extreme conditions. Examples of enzymes that break down and build up reactions are provided.

1. ENZYMES

2. ENZYMES
Proteins that function as biological catalysts

3. CATALYST
A substance that speeds up a chemical reaction and
is not changed by the reactions

5. ENZYMES LOWER ACTIVATION
ENERGY

6. PROPERTIES
 All enzymes are proteins
 Enzymes are made inactive by high
temperature
 Enzymes work best at a particular temperature
 Enzymes work best at a particular pH
 Enzymes are catalysts
 Enzymes are specific
 Enzymes are required in minute amounts

8. EXAMPLES OF ENZYMES
 Starch maltose
 Proteins amino acids
 Hydrogen peroxide water + oxygen
amylase
protease
These enzymes are also found in plants  in germinating seeds
catalase

9. BREAKDOWN REACTION

10. EXAMPLES OF ENZYMES
 Glucose starch
Starch phosphorylase
These enzymes are also found in plant cells

11. BUILDING UP REACTION

12. NICKNAMES
 Enzymes are named according to the reaction
that they catalyse.
Carbohydrases Proteases Lipase
Carbohydrates Proteins Lipid (fat)
Amylase Maltase Sucrase
Starch Maltose Sucrose
NOT ALL!!!

13. SUBSTRATES TO PRODUCTS
 A chemical reaction always involves one
substance changing into another
 Eq:
 Starch maltoseamylase

14. SUBSTRATE
The substance which is present at the beginning of
the reaction

15. PRODUCT
The substance which is made by the reaction

16. SPECIFIC
 The substrates of an enzyme are the
reactants that are activated by the enzyme
 Enzymes are specific to their substrates
 The specificity is determined by the active
site

17. ACTIVE SITE
Each enzyme can ONLY act on a particular kind of
substrate

18. THE LOCK AND KEY HYPOTHESIS
 Fit between the substrate and the active site of the enzyme
is exact
 Like a key fits into a lock very precisely
 The key is analogous to the enzyme and the substrate is
analogous to the lock.
 Temporary structure called the enzyme-substrate complex
formed
 Products have a different shape from the substrate
 Once formed, they are released from the active site
 Leaving it free to become attached to another substrate

19. LOCK AND KEY

20. TEMPERATURE
Temperature / °C
Enzyme
activity
0 10 20 30 40 50
Q10 Denaturation

22. TEMPERATURE
 Optimum temperature: 40–45oC
 Inactive at low temperature
 Kinetic energy low
 Collision of substrate to enzyme low
 Opposite when temperature is increased
 For every 10oC rise in temperature, the rate of enzyme
reaction is doubled, until the optimum temperature is
reached.

23. TEMPERATURE

24. pH
Optimum pH values
Enzyme
activity Trypsin
Pepsin
pH
1 3 5 7 9 11

26. USES
 Washing Powders : protease, lipases
 Food industry : pectinase, protease, amylase
 Medicine : antibiotics

27. ANTIBIOTICS
Substances which kill bacteria without harming
human cells
To cure bacterial infections

28. PENICILLIN
 Penicillium

29. Class Dicussion
 What makes a penicillin?
 Explain why air is bubbled through the
fermenter.
 Explain why water is made to run through a
jacket surrounding the fermenter
 Explain why the pH inside the fermenter is
controlled.