1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 8 An Introduction to Metabolism

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Energy of Life The living cell – Is a miniature factory where thousands of reactions occur CELL

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CELL ENERGY ENERGY Metabolism Is the totality of an organism’s chemical reactions Energy and Waste

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A metabolic pathway has many steps

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Catabolic pathways – Catabolic pathways: – Break down complex molecules into simpler compounds – Release energy ? ?

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Catabolic pathways – Catabolic pathways: – Break down complex molecules into simpler compounds – Release energy Monomers Polymers

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Anabolic pathways: – Build complicated molecules from simpler ones – Consume energy MonomersPolymer

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gibbs Free Energy (∆G) Examples: A + B = C – ∆G=+58 Kcal (REQUIRES 58 units of energy) D  E + F – ∆G = -37 Kcal (RELEASES 37units of energy)

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Exergonic reaction Release of Energy Spontaneous

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Endergonic reaction Requires Energy from its surroundings Non-spontaneous

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 8.3: How does ATP powers cellular work? Couples exergonic reactions to endergonic reactions

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and Hydrolysis of ATP ATP (adenosine triphosphate) – Is the cell’s energy shuttle – Provides energy for cellular functions

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Energy is released from ATP  ADP + P

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ATP hydrolysis can be coupled to other reactions Endergonic reaction: ∆G is positive, reaction is not spontaneous ∆G = +3.4 kcal/mol Glu + NH 3 NH 2 Glutamic acid Ammonia Glutamine

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ATP hydrolysis can be coupled to other reactions

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 8.4: Enzymes = catalytic protein – Speeds up reaction without being consumed by the reaction

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Substrate Specificity of Enzymes Enzyme Substrate Active Site Figure 8.16 Substate Active site Enzyme (a)

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Induced fit of a substrate (b) Enzyme- substrate complex Substate Active site Enzyme (a)

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The catalytic cycle of an enzyme Substrates Enzyme-Substrate Complex Enzyme Products

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Activation energy, E A – Initial amount of energy needed to start a chemical reaction

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The energy profile for an exergonic reaction

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The effect of enzymes on reaction rate SimSim Simulation: Cell Structure; Flash animate.; Transition State

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The active site can lower an E A barrier by: 1. Orienting substrates correctly 2. Straining substrate bonds 3. Providing a favorable microenvironment 4. Covalently bonding to the substrate Cell Structure; Flash; Enzymes; Proximity and Orientation

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Effects of Local Conditions on Enzyme Activity The activity of an enzyme is affected by general environmental factors: 1. Temperature 2. pH 3. Cofactors 4. Activators/Inhibitors

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Enzymes 1. Optimal Temperature

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2. Optimal pH

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 3. Cofactors Cofactors – Non-protein enzyme helpers Ex: Fe – Coenzymes- Organic cofactors Ex: vitamins

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 4. Enzyme Inhibitors and Activators Competitive inhibitors

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Noncompetitive inhibitors Simulation: Cell Res.; Enzyme tutorial; Enzyme inhibitors

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 8.5 Regulation of enzyme activity helps control metabolism

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Allosteric Regulation of Enzymes Allosteric regulation- protein’s function affected by binding of a regulatory molecule Active Inactive

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Allosteric Regulation of Enzymes Allosteric regulation- protein’s function affected by binding of a regulatory molecule Active Inactive Activator Inhibitor

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cooperativity- allosteric regulation that can amplify enzyme activity Simulation: Cell Res.; Enzyme tutorial; allosteric enzymes

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Feedback Inhibition Feedback inhibition – End product of a metabolic pathway shuts down the pathway

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Feedback inhibition

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Feedback inhibition

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Feedback inhibition

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Feedback inhibition Simulation: Cell Res.; Enzyme tutorial; Feedback Inhibition

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Review Chapter 8: Metabolic reactions: 1. Catabolic, spontaneous, exergonic reactions Ex: polymer  monomer 2. Anabolic, non-spontaneous, endergonic Ex: monomers  polymer

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Review Ch. 8 Gibbs Free Energy ΔG = ΔH - TΔS ATP exergonic rxn = ΔG = -7.3 Kcal/mole – How many ATP molecules will it take to run and endergonic rxn ΔG = 54.3 Kcal/mole? Enzymes: Lower E A  4 ways Affected by Environmental factors  4

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Review Ch. 8 Enzymes! Ch. 8 Enzymes! – Competitive vs. Noncompetitive Inhibitors – Allosteric Enzymes Activators, Inhibitors, Cooperativity Feedback Inhibition