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This is energy metabolism of living organisms.

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  1. 1. Biochemistry College of Life Sciences Zhejiang University Wei-Jun Yang Ph.D. 0571-88273176 ftp://marine:marine@
  2. 2. I IntroductionII Foundations of BiochemistryIII Structure and Catalysis and Information PathwaysV Bioenergetics and Metabolism
  3. 3. III Bioenergetics and Metabolism13 Principle of Bioenergetics14 Glycolysis and the Catabolism15 The Citric Acid Cycle16 Oxidation of Fatty Acid17 Amino Acid Oxidation and the Production of Urea18 Oxidative Phosphorylation and Photophosphrylation19 Carbohydrate Biosynthesis20 Lipid Synthesis21 Biosynthesis of Amino Acids, Nucleotides, and Related Molecules22 Integration and Hormonal Regulation of Mammalian Metabolism
  4. 4. Four Functions of Metabolism:1. To obtain chemical energy by capturing solar energy or by degradation of energy-rich nutrients from the environment .2. To convert nutrient molecules into the cells own characteristic molecules.3. To polymerize monomeric precursors into macrobiomolecules (proteins, nucleic acids, lipids, polysaccharides).4. To synthesize and degrade biomolecules required in specialized cellular functions.
  5. 5. Photosynthesis Cellular respiration Biological workThree Major Types of Energy Transformation
  6. 6. Biological Work Requires Energy
  7. 7. Hydrothermal vent(热液口)
  8. 8. Two Groups of Metabolism1. Autotrophs (自养生物,such as photosynthetic bacteria and higher plants) can use carbon dioxide from the atmosphere as their sole source of carbon, from which they construct all their carbon- containing biomolecules.2. Heterotrophs(异养生物)cannot use atmospheric carbon dioxide and must obtain carbon from their environment in the form of relatively complex organic molecules, such as glucose, proteins.
  9. 9. Energy relationships between catabolic and anabolic pathwaysCatabolism(异化作用):The pathway degrade organic nutrients intosimple end products in order to extract chemicalenergy and convert it into a form useful to the cell.Anabolism(同化作用):The pathway start with small precursor moleculesand convert them to larger and more complexmolecules and require the input of energy.
  10. 10. Energy relationships betweencatabolic and anabolic pathways
  11. 11. Three types of molecular metabolic pathwaysa; Converging catabolic b; Diverging anabolicc; Cyclic pathway
  12. 12. 14 Principle of Bioenergetics*** Bioenergetics and Thermodynamics*** Phosphoryl Group Transfers and ATP*** Biological Oxidation-Reduction Reaction
  13. 13. Biological Energy Transformations Follow the Laws of Thermodynamics Two Laws of Thermodynamics The First Law; The total energy in the universe does not change
  14. 14. The second Law;The entropy (disorder) of the universeis increasing
  15. 15. Biological Energy TransformationsFollow the Laws of Thermodynamics
  16. 16. Three thermodynamic quantities;1. Gibbs free energy (G) and free-energy change, ΔG2. Enthalpy (H) and Enthalpy change ΔH3. Entropy (S) and Entropy change ΔS
  17. 17. Gibbs Free Energy (G);expresses the amount of energy capable of doing workduring a reaction at constant temperature and pressure.Free-energy Change (ΔG);When ΔG° is negative, the products contain less freeenergy than the reactants. The reaction will thereforeproceed spontaneously to form the products understandard conditions.When ΔG° is positive, the products of the reactioncontain more free energy than the reactants. The reactionwill therefore tend to go in the reverse direction if we startwith 1.0 M concentrations of all components.The units of ΔG is joules/mole or calories/mole
  18. 18. Enthalpy (H,焓);is the heat content of the reacting system. It reflects thenumber and kinds of chemical bonds in the reactantsand products.Enthalpy Change (ΔH);When a chemical reaction releases heat, it is said to beexothermic; the heat content of the products is lessthan that of the reactants and ΔH has a negative value.Reacting systems that take up heat from theirsurroundings are endothermic and have positive valuesof ΔH.The units of ΔH is joules/mole or calories/mole
  19. 19. Entropy (S,熵);is a quantitative expression for the randomness ordisorder in a system.Entropy Change (ΔS);When the products of a reaction are less complex andmore disordered than the reactants, the reaction is saidto proceed with a gain in entropy (p. 72).The units ΔS is joules/mole•degree Kelvin.
  20. 20. In Biological Systems (at constant temperature and pressure) ΔG = ΔH - TΔST is the absolute temperature.When entropy increases, ΔS has a positive sign. Whenheat is released by the system to its surroundings, ΔHhas a negative sign. Either of these conditions, whichare typical of favorable processes, will tend to makeΔG negative. In fact, ΔG of a spontaneously reactingsystem is always negative.
  21. 21. Actual Free energy Changes Depend on the Concentration of Reactants and Products ΔG° = -RT ln Keq
  22. 22. 14 Principle of Bioenergetics*** Bioenergetics and Thermodynamics*** Phosphoryl Group Transfers and ATP*** Biological Oxidation-Reduction Reaction
  23. 23. ATP: Adenosin triphosphateADP: Adenosin diphosphateAMP: Adenosin monophosphate
  24. 24. Major Function of ATP in CellsHeterotrophic cells obtain free energy in a chemicalform by the catabolism of nutrient molecules and usethat energy to make ATP from ADP and Pi. ATP thendonates some of its chemical energy to endergonicprocesses such as the synthesis of metabolicintermediates and macromolecules from smallerprecursors, transport of substances across membranesagainst concentration gradients, and mechanicalmotion.
  25. 25. The Free-Energy Change for ATPHydrolysis Is Large and Negative
  26. 26. Although its hydrolysis is highly exergonic (ΔG° = -30.5 kJ/mol), ATP is kinetically stable towardnonenzymatic breakdown at pH 7 because theactivation energy for ATP hydrolysis is relatively high.Rapid cleavage of the phosphoric acid anhydride bondsoccurs only when catalyzed by an enzyme.
  27. 27. The actual free energy of hydrolysis (ΔG) of ATP in living cellsis very different (not 30.5 kJ/mol).Furthermore, the cytosol contains Mg2+, which binds to ATPand ADP. In most enzymatic reactions that involve ATP asphosphoryl donor, the true substrate is MgATP2- and therelevant ΔG° is that for MgATP2- hydrolysis. ΔG for ATP hydrolysis in intact cells, usually designated ΔGP, is much more negative than ΔG° in most cells ΔGP ranges from -50 to -65 kJ/mol.
  28. 28. Other Phosphorylated Compounds and Thioesters Also Have Large Free Energies of Hydrolysis1. Phosphoenolpyruvate(磷酸烯醇式丙酮酸)2. 1,3-bisphosphoglycerate(甘油-1,3-二磷酸)3. Phosphocreatine(磷酸肌酸)4. Thioesters(硫酯)
  29. 29. Other Phosphorylated Compounds and Thioesters Also Have Large Free Energies of Hydrolysis Phosphoenolpyruvate (磷酸烯醇式丙酮酸)
  30. 30. 1,3-bisphosphoglycerate (甘油-1,3-二磷酸)
  31. 31. Phosphocreatine(磷酸肌酸)
  32. 32. Thioesters(硫酯)
  33. 33. ATP Provides Energy by Group Transfers, Not by Simple Hydrolysis
  34. 34. Two groups of phosphate compounds in living organisms.High-energy compounds; ΔG° < -25 kJ/mol"low-energy" compounds; ΔG° > -25 kJ/mol Flow of Phosphoryl Groups
  35. 35. 14 Principle of Bioenergetics*** Bioenergetics and Thermodynamics*** Phosphoryl Group Transfers and ATP*** Biological Oxidation-Reduction Reaction
  36. 36. The transfer of phosphate groups is one of the centralfeatures of metabolism. Metabolic electron transferreactions are also of crucial importance.The path of electron flow in metabolism is complex.Electrons move from various metabolic intermediatesto specialized electron carriers in enzyme-catalyzedreactions. Those carriers in turn donate electrons toacceptors with higher electron affinities, with therelease of energy. Cells contain a variety of molecularenergy transducers, which convert the energy ofelectron flow into useful work.
  37. 37. The Flow of Electrons Can Do Biological Work
  38. 38. The energy made available to do work by thisspontaneous electron flow (the free-energy changefor the oxidation-reduction reaction) is proportionalto ΔE: ΔG=-nFΔE, or ΔG°=-nFΔE0
  39. 39. Acetaldehyde(乙醛)is reduced by NADH:Acetaldehyde + NADH + H+ ethanol + NAD+The relevant half reactions and their Eo values are:(1) Acetaldehyde + 2H+ + 2e- ethanol E0 = -0.197 V(2) NAD+ + 2H+ + 2e- NADH + H+ E0 = -0.320 VΔE0 = -0.197 V - (-0.320 V) = 0.123 V, and n is 2.ΔG° = -nFΔE0 = -2(96.5 kJ/V•mol)(0.123 V) = -23.7kJ/mol.
  40. 40. Soluble Electron Carriers1. Nicotinamide adenine dinucleotide (NAD+, 烟酰胺腺嘌呤二核苷酸)2. Nicotinamide adenine dinucleotide phosphate (NADP+,磷酸烟酰胺腺嘌呤二核苷酸)3. Flavin mononucleotide (FMN,黄素单核苷酸)4. Flavin adenine dinucleotide (FAD,黄素腺嘌呤 二核苷酸)
  41. 41. NADH and NADPH Act with Dehydrogenases (脱氢酶)as Soluble Electron Carriers
  42. 42. Flavoproteins Contain Flavin(黄素)Nucleotides
  43. 43. Topics for Next Chapter1. Glycolysis: two phases and ten steps of glycolysis (第6组)2. Three fates of pyruvate under aerobic and anaerobic conditions(第7组)3. Microbial fermentations yield alcohol and other end products of commercial value (第8组)4. Feeder pathways for glycolysis(第9组)5. Regulation of carbohydrate catabolism(第10组)6. The pentose phosphate pathway of glucose oxidation(第11组)