1. Chapter 8 An Introduction to Energy & Metabolism (Pages 141-159) Topics: Thermodynamic Laws Catabolism & Anabolism (metabolism) Exergonic vs. Endergonic Reactions Free Energy ATP Cycle & Energy Coupling Enzyme (structure & function)

2. Main Topics to Cover-Ch. 8 Potential vs. Kinetic Energy First Two Laws of Thermodynamics Entropy, Enthalpy, and Free Energy Endergonic vs. Exergonic Reactions Anabolism & Catabolism = Metabolism Energy Coupling: Oxidation/Reduction ATP; Structure & Function Enzymes Structure & Function- allosteric, feedback mechanisms

3. Energy is defined as the capacity to do work All organisms require energy to stay alive Energy makes change possible Energy is the capacity to perform work

4. Living cells are compartmentalized by membranes Membranes are sites where chemical reactions can occur in an orderly manner Living cells process energy by means of enzyme-controlled chemical reactions ENERGY AND THE CELL

5. Kinetic energy is energy that is actually doing work Potential energy is stored energy Figure 5.1A Figure 5.1B

6. Thermodynamics Energy (E)~ capacity to do work; Kinetic energy~ energy of motion; Potential energy~ stored energy Thermodynamics~ study of E transformations 1st Law: conservation of energy; E transferred/transformed, not created/destroyed 2nd Law: transformations increase entropy (disorder, randomness) Combo: quantity of E is constant, quality is not

7. First law of thermodynamics Energy can be changed from one form to another –However, energy cannot be created or destroyed Two laws govern energy conversion Figure 5.2A

8. Second law of thermodynamics Energy changes are not 100% efficient –Energy conversions increase disorder, or entropy –Some energy is always lost as heat Figure 5.2B

9. Metabolism/Bioenergetics Metabolism: The totality of an organism’s chemical processes; managing the material and energy resources of the cell Catabolic pathways: degradative process such as cellular respiration; releases energy Anabolic pathways: building process such as protein synthesis; photosynthesis; consumes energy

10. Equation Used to Determine Free Energy of a System  G =  H - T  S G: Quantity of Free Energy H: Enthalpy = System’s Total Energy (chemical Bond energy) T: Temperature (absolute temp. in Kelvin units) S: Entropy = Disorder of the system Spontaneous Reaction =  G will be negative (energy is released ie. Exergonic.) Non spontaneous Reaction (Endergonic)  G will be positive. What happens when  G is ZERO ???

12. Free Energy Free energy: portion of system’s E that can perform work (at a constant T) Exergonic reaction: net release of free E to surroundings (products have less free energy than reactants) Endergonic reaction: absorbs free E from surroundings (products have more free energy than reactants)

13. ATP & Energy Coupling See Pgs. 149-151

14. ATP is thought as the energy “currency” of a cell In cellular respiration, some energy is stored in ATP molecules ATP powers nearly all forms of cellular work ATP molecules are the key to energy coupling ATP shuttles chemical energy within the cell

15. General Facts about ATP Human use about 99 lbs of ATP each day @rest Every second 10 million ATP’s are made from ADP Bacteria has about a one-second supply of ATP

16. Energy Coupling & ATP Energy coupling: use of exergonic process to drive an endergonic one (ATP). Ex: Respiration (hydrolysis of glucose) is overall exergonic and will result in synthesizing ATP from ADP+P, which is endergonic Adenosine triphosphate (nucleotide w/3 PO 4 ’s) ATP tail: high negative charge ATP hydrolysis: release of free Energy Phosphorylation: binding of the released phosphate to another molecule

17. Introductory Questions #6 1)Explain how potential energy is different from kinetic energy. 2) Define each variable in the equation: ∆G = ∆H – T ∆S 3) What is the difference between an exergonic reaction and an endergonic reaction? 4)How is ATP associated with coupled reactions? What purpose does it serve? 5)How is an electron carried from one molecule to the next? Name a molecule that can carry an electron.

18. The Hydrolysis of ATP

19. When the bond joining a phosphate group to the rest of an ATP molecule is broken by hydrolysis, the reaction supplies energy for cellular work.  G = -32 KJ/mol (-7.6 Kcal/mol) Figure 5.4A Phosphate groups Adenine Ribose Adenosine triphosphate Hydrolysis Adenosine diphosphate (ADP) Energy

20. The ATP cycle Figure 5.4C Energy from exergonic reactions Dehydration synthesis Hydrolysis Energy for endergonic reactions

21. Example of Energy Coupling w/ATP Forming the Disaccharide Sucrose involves: glucose + fructose → sucrose (  G = +27 KJ/mol) ENDERGONIC Reaction Couple w/hydrolysis of ATP (  G = - 32KJ/mol) Occurs in a couple of reaction steps: Reaction#1: Glucose + ATP → glucose-P + ADP **glucose has been phosphorylated **ATP has been hydolyzed Reaction #2: Glucose-P + fructose → Sucrose + Pi (Pi is a low energy inorganic phosphate)

22. How ATP powers cellular work Figure 5.4B Reactants Potential energy of molecules Products Protein Work

23. Three Functions of ATP

24. Enzymes: Structure & Function See Pgs. 151-158

25. For a chemical reaction to begin, reactants must absorb some energy –This energy is called the energy of activation (EA) –This represents the energy barrier that prevents molecules from breaking down spontaneously Enzymes speed up the cell’s chemical reactions by lowering energy barriers

26. Enzymes Catalytic proteins: change the rate of reactions w/o being consumed Free E of activation (activation E): the E required to break bonds Substrate: enzyme reactant Active site: pocket or groove on enzyme that binds to substrate Induced fit model

27. A protein catalyst called an enzyme can decrease the energy barrier E A barrier Reactants 1Products2 Enzyme Figure 5.5A

28. Enzymes are selective –This selectivity determines which chemical reactions occur in a cell A Specific Enzyme Catalyzes each Cellular Reaction

29. How an Enzyme Works-Sucrase

30. How Enzymes Work http://www.ekcsk12.org/science/aplabrevie w/lab02.htmhttp://www.ekcsk12.org/science/aplabrevie w/lab02.htm **Description of Enzyme Lab Lab Simulation: http://bioweb.wku.edu/courses/Biol114/enzy me/enzyme1.asp

31. Effects on Enzyme Activity Temperature pH Cofactors: inorganic, nonprotein helpers; ex.: zinc, iron, copper Coenzymes: organic helpers ex. vitamins

32. Enzyme Inhibitors Irreversible (covalent); reversible (weak bonds) Competitive: competes for active site (reversible); mimics the substrate Noncompetitive: bind to another part of enzyme (allosteric site) altering its conformation (shape); poisons, many antibiotics

33. Inhibitors interfere with enzymes –A competitive inhibitor takes the place of a substrate in the active site –A noncompetitive inhibitor alters an enzyme’s function by changing its shape Enzyme inhibitors block enzyme action Substrate Enzyme Active site NORMAL BINDING OF SUBSTRATE Competitive inhibitor Noncompetitive inhibitor ENZYME INHIBITION Figure 5.8

34. Competitive & Noncompetitive Inhibitors

35. Enzyme activity is influenced by –temperature –salt concentration –pH Some enzymes require non-protein cofactors such as: Fe, Zn, Cu, etc. The Cellular environment affects enzyme activity

36. Certain pesticides are toxic to insects because they inhibit key enzymes in the nervous system Many antibiotics inhibit enzymes that are essential to the survival of disease-causing bacteria –Penicillin inhibits an enzyme that bacteria use in making cell walls Some Pesticides and Antibiotics inhibit Enzymes

37. Allosteric Enzymes-How they Work

38. Feedback Inhibition

39. Introductory Questions #6 1)Explain how potential energy is different from kinetic energy. What are some ways we can measure energy? 2) Define each variable in the equation: ∆G = ∆H – T ∆S 3) What is the difference between an exergonic reaction and an endergonic reaction? 4)How is ATP associated with coupled reactions? What purpose does it serve? 5)How is an electron carried from one molecule to the next? Name a molecule that can carry an electron.

40. Introductory Questions #7 1)Name three ways that enzyme activity can be measured as mentioned in your lab guidesheet. 2)Explain how the reactivity of pepsin is different from trypsin. (see pg. 154) 3)Give an two examples of a cofactor and two examples of a conenzyme. How are they different? 4)How is a competitive inhibitor different from a non-competitive inhibitor? 5)What is an allosteric enzyme?