1. Chapter 16.6 & 16.7 Enzymes & Enzyme Actions
SWBAT:
Describe how enzymes function as catalysts and give their names
Describe the role of an enzyme in an enzyme-catalyzed reaction

2. Introduction to Enzymes
Biological catalyst which speed up biological reactions by lowering the activation energy required for them to take place
Mostly made up of proteins
Mot used up or chemically change at the end of the biological reaction
What is an enzyme?

3. Introduction to Enzymes
Can be used again and again
Produced only when needed
Catalyse reversible reactions
E + S ES EP E + P
E = enzyme
S = substrate
P = product
How enzymes work?

4. Names of Enzymes
Name describes the compound or reaction that is catalyzed
Name is derived by replacing the end of the name with –ase
Example:
Oxidation Reaction = oxidase
Dehydration Reaction - dehydronase

5. Names of Enzymes Some early known enzymes end in –in
pepsin, rennin, trypsin
Recently, classifying and naming enzymes based on the type of reaction is catalyzes

6. Classification of Enzymes
Oxidoreductoases (Oxidation – Reduction)
Transferases (Transfer groups of atoms)
Hydrolases (Hydrolysis)
Carbohydrases, Proteases, Lipases
Lyases (Add/Remove atoms to/from a double bond)
Isomerases (Rearrange atoms)
Ligases (Combine molecules using ATP)

7. Enzyme Action Enzymes are globular proteins
Unique 3-D shape that binds to a small group of reacting molecules called substrates

8. Active Site
Area where the enzyme binds the substrate and catalyzes the reaction
The active site of a particular enzyme fits the shape of only a few types of substrates
Substrate
Active Site

9. Enzyme-Catalysed Reactions
Anabolic reactions
Synthesis is simpler substances into complex substances
Amino Acids  Polypeptides  Proteins
Catabolic reactions
Breakdown of complex substance into more simple substances
Hydrogen peroxide  Oxygen + Water
2 H2O2  O2 + 2 H2O

10. Characteristics of Enzymes
Speed up chemical reactions
Small amount needed to catalyse a reaction because enzymes can be used again and again
The shapes of the active sites make enzymes highly specific, meaning they can only interact with 1 type of substrate to form an enzyme-substrate complex

11. “Lock and Key” Hypothesis
The active site of an enzyme molecule = lock; substrate molecule that the enzyme acts on = key
When the enzyme and substrate molecules are bound together, they form an enzyme-substrate complex

12. “Lock and Key” Hypothesis (cont.)
Substrate molecule is subsequently converted into products
Product molecules leave the active site
Enzyme molecule is free to bind with more substrate molecules

13. “Induced Fit” Model
Enzyme molecule can undergo adjustments at its active site
Binds more tightly with substrate molecule
Facilitates binding at active site and speeds up rate of chemical reaction

14. Chapter 16.8 Factors Affecting Enzyme Activity
SWBAT:
Describe the effect of temperature, pH, concentration of
substrate and inhibitors on enzyme activity

15. Factors Which Affect Enzyme Activity
Temperature pH
Concentrations of substrates in enzymatic reactions

16. Temperature
Optimum temperature (37°C) – the temperature at which an enzyme is most active (can catalyze the most number of reactions per second)
Rise in temperature (until optimum) 
Increase in enzyme activity
Kinetic energy of particles increases
Increases chance of substrate molecules fitting into the active sites of enzyme molecules
More rapid formation of enzyme-substrate complexes
Increase in formation of products

17. Temperature (cont.)
When temperature exceeds optimum temperature of enzyme activity, it starts to fall rapidly
H-H bonds in enzymes break, leading to the denaturation of enzymes
Unique 3-D structure lost
Denaturation is irreversible

18. pH Optimum pH (~7.4) = maximum activity
Most enzymes lose their abilities to catalyse reactions at pH 3 and pH 11
Extreme changes in pH of a solution will denature the enzyme, just like temperature

19. pH (cont.)
Slight changes in pH is enough to change the electrostatic charges of the active site of enzyme and substrate
Electrostatic repulsion occurs
Inhibits the formation of enzyme-substrate complex

20. Substrate & Enzyme Concentrations
Substrate concentration increases  rate of reaction increases
Saturation of enzyme molecules (all being made use of in reaction)
Reaction cannot take place
Increase in enzyme concentration will increase the rate of reaction again

21. Animation Animation comparing Link to animation Enzymes Substrates
Inhibitors
Temperature pH
Link to animation

22. Enzyme Inhibitor

23. Competitive Inhibition

24. Non-Competitive Inhibition