1. Bio 178 Lecture 14 Metabolism and Respiration http://www.nicertutor.com/doc/class/bio100/Locked/media/ch07/DB07040.jpg

2. Reading Chapters 8 & 9 Quiz Material Questions on P 158 & 184 Chapters 8 & 9 Quizzes on Text Website (www.mhhe.com/raven7)

3. Outline Energy and Metabolism ð Enzymes (cntd.) Cellular Respiration

4. Environmental Effects on Enzyme Catalysis Affected by anything that alters its 3D shape: pH, [salt], temperature, regulatory molecules Temperature Optimum Temperature Temperature at which reaction rate is greatest. Below Optimum Increasing temp increases substrate-enzyme collisions & can stress bonds. Bonds not flexible to permit induced fit  not optimum. Above Optimum Denaturation.

5. Effect of Temperature on Enzyme Catalysis

6. Environmental Effects on Enzyme Catalysis pH Optimum pH pH at which reaction rate is greatest. Above/Below Optimum Change in [H + ] affects charge balance between charged amino acids, which affects intramolecular bonding.

7. Effect of pH on Enzyme Catalysis

8. Molecules that Regulate Enzyme Action 1. Inhibitors Bind to enzymes to decrease their activity. Function Regulation of metabolic pathways, eg. Feedback inhibition. Inhibitory Mechanisms (a) Competitive Inhibitors Compete with the substrate for the active site. (b) Noncompetitive Inhibitors Bind to enzyme in a regulatory site other than the active site  conformational change. Eg. Allosteric site - “on/off switches”

9. Mechanisms of Enzyme Inhibition

10. Molecules that Regulate Enzyme Action 2. Activators Bind to enzymes to increase their activity. Usually bind to allosteric sites.

11. Enzyme Cofactors Non-protein “helpers” that aid in some enzyme catalyzed reactions. How do they Work? Draw electrons away from covalent bonds in the substrate  weaken bonds. Inorganic Cofactors Example - Metal ions like zinc, molybdenum, & manganese. Coenzymes Non-protein organic cofactors, eg. Vitamins.

12. Coenzymes and Redox Reactions Coenzymes (electron acceptors) shuttle energy from one enzyme to the next - pass energy with pairs of electrons from one substrate to the next in a reaction series. Example: Nicotinamide adenine dinucleotide (NAD + ) Composition 2 nucleotides (NMP + AMP). Functions of its constituent parts AMP - Core (conformation recognized by enzyme) NMP - Electron acceptor Reduction of NAD + NAD + + 2H  NADH + H + (2 electrons & 1 H + transferred to NAD + )

13. Structure of NAD +

14. Biochemical Pathways - Metabolism Anabolic Reactions Biosynthetic part of metabolism - Energy expended to synthesize materials. Catabolic Reactions Part of metabolism involved in hydrolyzing macromolecules - usually harvest energy. Biochemical Pathways Sequences in which the products of one enzyme controlled reaction are the substrates for the next in a series of reactions.

15. Biochemical Pathways McGraw-Hill Video

16. Regulation of Biochemical Pathways Why Regulate? Save energy when a product is not needed. How is Regulation Achieved? Feedback inhibition.

17. Feedback inhibition

18. Feedback Inhibition McGraw-Hill Video

20. How do Organisms Obtain Energy? Chemical bonds contain energy - these bonds must be broken to extract the energy. Energy (potential) is obtained from the electrons in the bond. Step 1 - Digestion Enzymes break the large molecules into smaller ones. Step 2 - Catabolism Enzymes break down the smaller molecules step by step, harvesting energy at each step.

21. Cellular Respiration The metabolic harvesting of energy by oxidation. The electrons (&  the energy) are transferred from one molecule to the next, losing energy as they go. Types of Cellular Respiration Aerobic Final electron acceptor is oxygen. Anaerobic Final electron acceptor is an inorganic molecule other than oxygen. Fermentation Final electron acceptor is an organic molecule.

22. Cellular Respiration (Cntd.) Overall Reaction C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + Energy ∆G -720 kcal/mole of glucose (cellular conditions) Negative sign: Products contain less energy than reactants. Where does the Energy Released Go? Cells harvest some of it to make ATP. The rest is released as heat.

23. Using ATP to Provide Energy How is energy released from ATP? The transfer of a phosphate group to another molecule relaxes the ATP (electrostatic repulsion).

24. ATP Synthase Makes most of the ATP produced by the cell. What is the energy source for ATP synthase? Protons diffuse into the cell through ATP synthase. This releases energy. The energy is used by ATP synthase to rotate. This mechanical energy is converted to chemical energy by adding a third phosphate to ADP.

25. ATP Synthase

26. Glucose Catabolism Methods for Making ATP 1. Substrate-Level Phosphorylation ADP + P i  ATP P i comes from a phosphate bearing intermediate molecule. Example - Glycolysis. 2. Aerobic Respiration ATP synthase makes ATP using energy provided by electron transfer. O 2 = final electron acceptor.

27. Substrate-Level Phosphorylation

28. Aerobic Respiration

29. Processes Involved in Eukaryotic Respiration 1. Glycolysis Sugar splitting anaerobic process. Location Cytoplasm Energetic Products 2 ATP net & 2 NADH net produced by substrate level phosphorylation. 2. Aerobic Respiration Pyruvate oxidation Krebs cycle Electron transport chain