1. Amino Acids, Proteins, and Enzymes
Enzymes Enzyme Action Factors Affecting Enzyme Action Enzyme Inhibition

2. Enzymes Catalysts for biological reactions Most are proteins
Catalyst: Substance that speeds up a chemical reaction without being used in the process
Most are proteins
Lower the activation energy
Minimum energy required to start a reaction
Increase the rate of reaction

4. Enzyme Action and the Hydrolysis of Sucrose
Enzyme Sucrase breaks down a molecule of sucrose into glucose and
fructose

5. What do enzyme names tell us?
Enzyme names usually end in –ase
Identifies a reacting substance
sucrase – breaks down sucrose
lipase - breaks down lipids
Describes function of enzyme
oxidase – catalyzes oxidation
hydrolase – catalyzes hydrolysis
Common names of digestion enzymes still use –in
ex. pepsin, trypsin
What do you think lactase does? …Manon???

6. Important Enzyme Terms
Substrate: Reactant(s) an enzyme is acting on
ex. what is the substrate sucrase acts on?
Active Site: The location on the enzyme where the substrate binds
Enzyme-Substrate Complex: An enzyme with its substrate attached to the active site

7. 2 Models for Enzyme Action
Lock and Key Model
Induced Fit Model

8. Enzyme Action: Lock and Key Model
An enzyme binds a substrate in a region called the active site
Only certain substrates can fit the active site
Amino acid R groups in the active site help substrate bind
Enzyme-substrate complex forms
Substrate reacts to form product
Product is released

9. Lock and Key Model

10. Lock and Key Model

11. Lock and Key Model
E S ES complex E P P S S P

12. Enzyme Action: Induced Fit Model
Enzyme structure flexible, not rigid
Enzyme and active site adjust shape to bind substrate
Increases range of substrate specificity
Shape changes also improve catalysis during reaction

13. Enzyme Action: Induced Fit Model
E S ES complex E P P S S S P

15. Learning Check The active site is (1) the enzyme
(2) a section of the enzyme
(3) the substrate
B. In the induced fit model, the shape of the enzyme when substrate binds
(1) Stays the same
(2) adapts to the shape of the substrate

16. Solution E2 The active site is (2) a section of the enzyme
B. In the induced fit model, the shape of the enzyme when substrate binds
(2) adapts to the shape of the substrate

17. Practice Questions
Complete the 2 practice questions at the end of the worksheet with a partner

18. Factors Affecting Enzyme Action: Temperature
Little activity at low temperature
Rate increases with temperature
Most active at optimum temperatures (usually 37°C in humans)
Activity lost with denaturation at high temperatures

19. Factors Affecting Enzyme Action
Optimum temperature
Reaction
Rate
Low High
Temperature

20. Factors Affecting Enzyme Action: Substrate Concentration
Increasing substrate concentration increases the rate of reaction (enzyme concentration is constant)
Maximum activity reached when all of enzyme combines with substrate

21. Factors Affecting Enzyme Action
Maximum activity
Reaction
Rate
substrate concentration

22. Factors Affecting Enzyme Action: pH
Maximum activity at optimum pH
The pH affects the R group of the amino acid
Changing the pH changes the charge on R groups which changes the tertiary structure of the enzyme
Different enzymes have a different optimal pH
Pepsin works best at a pH of 2 (found in the stomach)
Trypsin works best at a pH of 8 (found in small intestine)
Most lose activity in low or high pH

23. Factors Affecting Enzyme Action
Reaction
Rate
Optimum pH pH

24. Learning Check E3
Sucrase has an optimum temperature of 37°C and an optimum pH of 6.2. Determine the effect of the following on its rate of reaction (1) no change (2) increase (3) decrease A. Increasing the concentration of sucrose B. Changing the pH to 4 C. Running the reaction at 70°C

25. Solution E3
Sucrase has an optimum temperature of 37°C and an optimum pH of 6.2. Determine the effect of the following on its rate of reaction (1) no change (2) increase (3) decrease A. 2, 1 Increasing the concentration of sucrose B. 3 Changing the pH to 4 C. 3 Running the reaction at 70°C

26. Potato Lab How do these factors relate to the lab we are doing today?
What is the enzyme in this lab?
What is the substrate in this lab?
Which factors affecting enzyme action are we manipulating?

27. Time to Plan!
As a group you need to design the procedure for the second half of the lab
When your group has agreed on the procedure share it with me for approval
Once it is approved everyone needs to write the procedure into their lab handout
All written procedures, observations, and questions need to be completed in your own words

28. Safety Precautions
What safety precautions do you think are necessary for this lab?
Materials:
3% Hydrogen Peroxide (purchased at the drug store, used as a disinfectant for cuts)
Potato blended with water

29. Enzyme Inhibition Inhibitors cause a loss of catalytic activity
Change the protein structure of an enzyme
May be competitive or noncompetitive
Some effects are irreversible

30. Competitive Inhibition
A competitive inhibitor
Has a structure similar to substrate
Occupies active site
Competes with substrate for active site
Has effect reversed by increasing substrate concentration

32. Noncompetitive Inhibition
A noncompetitive inhibitor
Does not have a structure like substrate
Binds to the enzyme but not active site
Changes the shape of enzyme and active site
Substrate cannot fit altered active site
No reaction occurs
Effect is not reversed by adding substrate

34. Learning Check E4
Identify each statement as describing an inhibitor that is
(1) Competitive (2) Noncompetitive
A. Increasing substrate reverses inhibition
B. Binds to enzyme, not active site
Structure is similar to substrate
D. Inhibition is not reversed with substrate

35. Solution E4 Identify each statement as describing an inhibitor that is
(1) Competitive (2) Noncompetitive
A Increasing substrate reverses inhibition
B Binds to enzyme, not active site
C Structure is similar to substrate
D Inhibition is not reversed with substrate

36. Allosteric Regulation

37. Allosteric Regulation
Allosteric Regulation: A method used by cells to control enzyme activity
Allosteric Sites:
A receptor site that is located some distance from the active site
Binds substances that inhibit or stimulate an enzyme’s activity
Activator: Binding to allosteric site on enzyme stabilizing the protein conformation keeping the active site available for the substrate
Allosteric Inhibitor: Binding to allosteric site on enzyme stabilizing the protein conformation keeping the active site UNavailable for the substrate
…Does this sound familiar???

40. Applications of Enzymes
Used in laundry detergents!
Combincation of Proteases, Lipases, and Amylases
Lactase for lactose intolerant people!
Can be eaten in a pill
Milk/dairy products can be pre-treated
Meat Tenderizer
Protease can be added to tough cuts of meat to make the meat more tender
Contact Lens Solution
Proteases and lipases added to get rid of dirt

41. Homework: Use of Enzymes- Reading
Answer the questions on the question sheet using the information in the reading

42. Homework: Complete your portfolio for Unit 1

43. Unit Test: Biochemistry
There are review questions on the website
I will also post the review questions created by your peers
Will be next Saturday at the start of class
Will cover all the material we have discussed in the biochemistry unit (including questions from your lab!)
If you are unclear about any of these concepts please me!