1. Enzymes 1.7

2. Enzymes proteins produced by cells biological catalysts speed up chemical reactions without being consumed

3. Activation Energy (E A ) all chemical reactions require an initial input of energy, called activation energy (E A )

4. Enzymes and E A

5. Activation Energy enzymes increase the rate of a reaction by lowering the activation energy (E A ) How?

6. What are enzymes? enzymes are globular proteins that act on substrates (reactants) substrates bind to specific sites (active sites) on enzymes, creating the enzyme- substrate complex

7. Enzyme-Substrate Complex

8. Induced-Fit Model in the “induced-fit” model, the enzyme alters shape to better “fit” substrate “lock and key” model

9. And then what? 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

10. Example: Sucrase Image from: http://awesomebiology.wikispaces.com/Enzymes

11. What do these enzymes do? 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)

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

13. Animation Activation Energy & Enzymes: http://www.sumanasinc.com/webcontent/ani mations/content/enzymes/enzymes.html

14. Cofactors and Coenzymes some enzymes require cofactors to function as catalysts cofactors are non-protein molecules or inorganic ions coenzymes are organic cofactors

15. Cofactors

16. Factors Affecting Rate of Enzyme Activity substrate concentration enzyme concentration temperature pH

17. Enzyme Regulation

18. Competitive Inhibition

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

20. Allosteric Regulation some enzymes have allosteric sites (receptor sites away from the active site) allosteric sites can bind substances that inhibit or stimulate an enzyme’s activity

21. Allosteric Regulation

23. allosteric activators promote the action of the enzyme allosteric inhibitors prevent the action of the enzyme (i.e. non-competitive inhibition)

24. Feedback Inhibition (Image from: http://classes.midlandstech.edu/carterp/Courses/bio225/chap05/ss2.htm) can be used to regulate multi-step metabolic pathways the end product of a pathway acts as an allosteric inhibitor of the first enzyme of the pathway http://highered.mcgraw- hill.com/sites/0072437316/student _view0/chapter8/animations.html#http://highered.mcgraw- hill.com/sites/0072437316/student _view0/chapter8/animations.html#

25. Homework (p.57) #1 What is a substrate and active site? How are they related? Why is an enzyme considered a biological catalyst?

26. Homework (p.57) #2,3 Describe the induced-fit hypothesis of enzyme-substrate interaction. 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.

27. Homework (p.57) #5 How does the rate of a 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

28. Homework (p.57) #8,9 Describe the different effects of an activator and an inhibitor on an allosterically regulated enzyme. Describe how feedback inhibition reduces the waste of cellular resources.

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

30. 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.

31. Commercial Uses of Enzymes (Image from: http://housewares.hardwarestore.com/35-176-laundry-detergents.aspx) cheese lactose-free dairy products cheese corn & wheat syrup sweeteners etc.