1. Enzymes
1.7 & 3.3

2. Enzymes biological catalysts
speed up chemical reactions without being consumed
usually proteins with tertiary or quaternary structure
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FYI: This enzyme is the insulin-degrading enzyme, control of which might help to cure Alzheimer’s disease.

3. Enzyme Action enzymes bind to specific reactants called substrates
substrates bind to active sites on enzymes, forming the enzyme-substrate complex

4. Enzyme-Substrate Complex
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5. Induced-Fit Model
in the “induced-fit” model, the enzyme alters its shape to better “fit” substrate
contrast with the “lock and key” hypothesis
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Interactions between functional groups of enzyme & substrate cause enzyme to alter shape to better fit substrate

6. Example: Sucrase
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7. What reactions do these enzymes catalyze?
lactase
breaks down lactose (sugar found in milk)
ATPase
breaks off a phosphate group from ATP, resulting in ADP + an inorganic phosphate + energy
amylase
breaks down starch (in saliva & intestine)

8. What about this one? ATP synthase
synthesizes ATP from ADP and inorganic phosphate

9. Cofactors and Coenzymes
some enzymes require cofactors to function as catalysts
cofactors are non-protein molecules or inorganic ions
coenzymes are organic cofactors
Cofactors: Zn, Fe ions, etc.
Coenzymes: NAD, FAD, CoA, etc. 9

10. Cofactors 10

11. Homework (p.57) #3
What is the functional role of a coenzyme or a cofactor in an enzyme-induced reaction? Give an example of an enzyme that requires a cofactor or coenzyme.

12. Factors Affecting Rate of Enzyme Activity
substrate concentration
enzyme concentration
temperature pH
Increasing the substrate concentration increases the reaction rate to a certain point. Once the enzymes are saturated with substrate, the concentration of enzyme becomes the limiting factor.
Protein (enzyme) folding depends on interactions between amino acid side (R) groups, some that are acidic or basic. Each protein (enzyme) has an optimal pH at which they fold correctly.
Temperature – At high temperatures, enzymes become denatured and don’t function. At low temperatures, enzymes are too rigid to catalyse a reaction. Enzymes usually function best at body temperature (37C in humans).

13. Homework (p.57) #5
How does the rate of reaction change as a result of each of the following factors? (Support your answer with a graphic representation of the enzymatic rates.)
enzyme concentration
substrate concentration
temperature pH

14. Homework (p.57) #10
Why is it important for the human body to maintain a proper temperature and a proper pH at all times?

15. Enzyme Regulation 15

16. Competitive Inhibition16

17. Competitive Inhibition
competitive inhibitors
have a similar structure to the substrate
bind to the enzyme’s active site and block the substrate from binding 17

18. Irreversible Inhibitors
Many drugs & pesticides act as irreversible inhibitors of enzymes
cyanide (inhibits key enzyme in cellular respiration)
antibiotics (inhibit bacterial enzymes)

19. Allosteric Regulation
some enzymes have allosteric sites
allosteric regulators either inhibit or stimulate an enzyme’s activity 19

20. Allosteric Regulation

21. Allosteric Regulation21

22. Allosteric Regulation
allosteric activators promote the action of the enzyme
allosteric inhibitors prevent the action of the enzyme (i.e. noncompetitive inhibition) 22

23. Homework (p.57) #6, 8
Describe noncompetitive inhibition. Provide an example to support your answer.
Describe the different effects of an activator and an inhibitor on an allosterically regulated enzyme.

24. Feedback Inhibition
often used to regulate multi-step metabolic pathways
the product of a pathway usually acts as an allosteric inhibitor of the first enzyme of the pathway 24

25. (Image from: http://classes. midlandstech25

26. Commercial Uses of Enzymes
cheese
lactose-free dairy products
corn & wheat syrup sweeteners
etc.
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Starch-processing into glucose through enzyme-catalyzed hydrolysis
Cheese manufacturing involves enzymes called proteases (rennet) and lipases
Dairy products without lactose.
Detergents often contain proteases and amylases to remove protein and carbohydrate stains.

27. Homework (p.57) #11
You are making a gelatin dessert, but the directions tell you not to use fresh pineapple because the gelatin will not solidify. Pineapple contains an enzyme, bromelain, which is a protease.
What effect does a protease have on a protein like collagen?
Could you use cooked or canned pineapple instead? Explain your answer.

28. Homework (p.57) #12
Humans produce enzymes in the mouth, stomach, and small intestine that aid in the process of digestion. As we age, we tend to produce less of these enzymes. What effect could this have on digestion and nutrition?

29. Activation Energy (EA)
all chemical reactions require an initial input of energy, called activation energy (EA)
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Recall collision theory from Grade 10 Science 29

30. Enzymes & Activation Energy
3.3

31. Enzymes and EA
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32. Activation Energy
enzymes increase the rate of a reaction by lowering the activation energy (EA)
How? 32

33. How is Ea reduced? weak bonds form between substrate and enzyme
enzyme provides proper orientation of substrate(s)
enzyme puts strain on bonds of substrate(s), making them easier to break 33

34. Animation Activation Energy & Enzymes: 34