Ground Rules of Metabolism

1. Ground Rules of Metabolism Chapter 6

2. Free Radicals • Unbound molecular fragments with the wrong number of electrons • Highly reactive • Can disrupt structure of molecules

3. Keeping Free Radicals in Check superoxide dismutase catalase Figure 6.1Page 96

4. Superoxide Dismutase • Catalyzes the formation of hydrogen peroxide from oxygen-free radicals and hydrogen ions • Accumulation of hydrogen peroxide can be lethal to cells

5. Catalase Catalyzes the formation of oxygen and water from hydrogen peroxide 2H2O2 ----------> 2H2O + O2

6. What Is Energy? • Capacity to do work • Forms of energy • Potential energy • Kinetic energy • Chemical energy

7. What Can Cells Do with Energy? • Cells use energy for: • Chemical work • Mechanical work • Electrochemical work

8. First Law of Thermodynamics • The total amount of energy in the universe remains constant • Energy can undergo conversions from one form to another, but it cannot be created or destroyed

9. One-Way Flow of Energy • The sun is life’s primary energy source • Producers trap energy from the sun and convert it into chemical bond energy • Allorganisms use the energy stored in the bonds of organic compounds to do work

10. Second Law of Thermodynamics • No energy conversion is ever 100 percent efficient • The total amount of energy is flowing from high-energy forms to forms lower in energy

11. Entropy • Measure of degree of disorder in a system

12. Energy Changes & Cellular Work Energy changes in cells tend to run spontaneously in the direction that results in a decrease in usable energy

13. Endergonic Reaction glucose - a product with more energy + 602 and 6H2O Energy in energy-poor starting substances 6 12 Figure 6.5a,bPage 100

14. Exergonic Reaction glucose - energy-rich starting substance + 602 Energy out 6 6 products with less energy Figure 6.5a,bPage 100

15. Structure of ATP nucleotide base (adenine) three phosphate groups sugar (ribose) Figure 6.6bPage 101

16. ATP: Main Energy Carrier • ATP/ADP cycle regenerates ATP ATP energy output energy input ADP + Pi

17. Electron Transfers • Oxidation - lose electron • Reduction - gain electron • Central to the formation of ATP during photosynthesis and aerobic respiration

18. Energy Carriers Enzymes Cofactors Participants in Metabolic Pathways • Reactants • Intermediates • Products

19. Degradative and Anabolic Pathways large energy-rich molecules ADP + Pi BIOSYNTHETIC PATHWAYS (ANABOLIC) DEGRADATIVE PATHWAYS (CATABOLIC) ATP simple organic compounds energy-poor products ENERGY INPUT

20. Types of Reaction Sequences A B C D E F LINEAR PATHWAY CYCLIC PATHWAY G K J I BRANCHING PATHWAY N M L H Figure 6.8Page 102

21. Which Way Will a Reaction Run? • Nearly all chemical reactions are reversible

22. Chemical Equilibrium RELATIVE CONCENTRATION OF REACTANT RELATIVE CONCENTRATION OF PRODUCT HIGHLY SPONTANEOUS EQUILIBRIUM HIGHLY SPONTANEOUS Figure 6.9Page 103

23. Chemical Equilibrium • Energy in the reactants equals that in the products • Product and reactant molecules usually differ in energy content • Therefore, at equilibrium, the amount of reactant almost never equals the amount of product

24. No Vanishing Atoms • Law of conservation of mass • Reactions rearrange atoms, but they never destroy them • As many atoms of each element in all the products as there were in all the reactants

25. Electron Transfer Chains • Arrangement of enzymes, coenzymes, at cell membrane • Works like a bucket brigade in fighting fires in that electrons are transferred from a carrier to the next in the cell membrane.

26. Enzyme Structure and Function Enzymes are catalytic molecules They speed the rate at which reactions approach equilibrium

27. Four Features of Enzymes 1) Enzymes do not make anything happen that could not happen on its own. They just make it happen much faster. 2) Reactions do not alter or use up enzyme molecules.

28. Four Features of Enzymes 3) The same enzyme usually works for both the forward and reverse reactions. 4) Each type of enzyme recognizes and binds to only certain substrates.

29. Activation Energy • For a reaction to occur, an energy barrier must be surmounted • Enzymes make the energy barrier smaller activation energy without enzyme starting substance activation energy with enzyme energy released by the reaction products Figure 6.12aPage 105

30. Factors Influencing Enzyme Activity Coenzymes and cofactors regulators Temperature pH Salt concentration

31. Effect of Temperature • Small increase in temperature increases molecular collisions, reaction rates • High temperatures disrupt bonds and destroy the shape of active site Figure 6.17bPage 109

32. Effect of pH Figure 6.17cPage 109

33. Beer, Enzymes, and Your Liver • Alcohol dehydrogenase • Acetaldehyde dehydrogenase • Cytochrome and catalase • Heavy drinking destroys liver cells and body’s ability to detoxify alcohol