Chemistry 501 Handout 13 Bioenergetics and Biochemical Reaction Types Chapter 13Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Chemistry 501 Handout 13Bioenergetics and Biochemical Reaction TypesChapter 13Dep. of Chemistry & BiochemistryProf. IndigLehninger. Principles of Biochemistry.by Nelson and Cox, 5th Edition; W.H. Freeman and CompanyG = Go + RT ln QG = H - TSThe usual source of free energy in coupled biologicalreactions is the energy released by hydrolysis ofphosphoanhydride bonds, such as those of adenosinetriphosphate (ATP).G > 0 ---> nonspontaneous process (endergonic)G < 0 ---> spontaneous process (exergonic)G = 0 ---> equilibrium (Go = - RT ln Keq)Cell function depends largely on molecules, such as proteins and nucleic acids, for which the free energy of formation is positive. To carry out these thermodynamically unfavorable reactions, cells couple them to other reactions that liberate free energy, so that the overall process is exergonic.Energy coupling links reactions in biologyaA + bB <--> cC + dDG = G’o + RT ln [C]c[D]d[A]a[B]bG’o = - RT ln k’eqEnergy coupling in mechanical and chemical processesG = G’o + RT ln [C]c[D]d[A]a[B]bmass-action ratio, QThe direction of the reaction towards equilibrium (as well as the actual reactionG) depends on QG = G’o + RT ln [C]c[D]d[A]a[B]bThe central role of ATP in metabolismThe free energy change for ATP hydrolysis is large and negativeThe direction of the reaction towards equilibrium (as well as the actual reactionG) depends on QGp = G’o + RT ln [ADP] [Pi][ATP]= -52 kJ/molphosphorylation potentialG = G’o + RT ln [C]c[D]d[A]a[B]bmass-action ratio, QOther phosphorilated compoundsand thioesters also have large freeenergies of hydrolysisATP HydrolysisRanking of biological phosphate compoundsby standard free energies of hydrolysisATP provides energy by group transfer, not by simple hydrolysisATP donates phosphoryl, pyrophosphoryl, and adenylyl groupsTransphosphorylations between nucleotides occur in all cell typesBiological oxidation-reduction reactionsE = E’o + RT/nF ln [acceptor]/[donor]E’o = E’o (electron acceptor) - E’o (electron donor) G’o = - nF E’oA few types of coenzymes and proteins serve as universal electron carriersNicotinamide adenine dinucleotideA few types of coenzymes and proteins serve as universal electron
View Full Document