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Chemistry 501 Handout 13 Bioenergetics and Biochemical Reaction Types Chapter 13

Dep. of Chemistry & Biochemistry Prof. Indig. Chemistry 501 Handout 13 Bioenergetics and Biochemical Reaction Types Chapter 13. Lehninger. Principles of Biochemistry. by Nelson and Cox, 5 th Edition; W.H. Freeman and Company. Energy coupling links reactions in biology.

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Chemistry 501 Handout 13 Bioenergetics and Biochemical Reaction Types Chapter 13

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  1. Dep. of Chemistry & Biochemistry Prof. Indig Chemistry 501 Handout 13Bioenergetics and Biochemical Reaction TypesChapter 13 Lehninger. Principles of Biochemistry. by Nelson and Cox, 5th Edition; W.H. Freeman and Company

  2. Energy coupling links reactions in biology 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. The usual source of free energy in coupled biological reactions is the energy released by hydrolysis of phosphoanhydride bonds, such as those of adenosine triphosphate (ATP). DG = DH - TDS DG = DGo + RT ln Q DG > 0 ---> nonspontaneous process (endergonic) DG < 0 ---> spontaneous process (exergonic) DG = 0 ---> equilibrium (DGo = - RT ln Keq)

  3. DG = DG’o + RT ln [C]c[D]d [A]a[B]b aA + bB <--> cC + dD DG’o = - RT ln k’eq

  4. DG = DG’o + RT ln [C]c[D]d [A]a[B]b DG = DG’o + RT ln [C]c[D]d [A]a[B]b mass-action ratio, Q Energy coupling in mechanical and chemical processes The direction of the reaction towards equilibrium (as well as the actual reaction DG) depends on Q

  5. The central role of ATP in metabolism The free energy change for ATP hydrolysis is large and negative

  6. DG = DG’o + RT ln [C]c[D]d [A]a[B]b mass-action ratio, Q DGp = DG’o + RT ln [ADP][Pi] = -52 kJ/mol [ATP] The direction of the reaction towards equilibrium (as well as the actual reaction DG) depends on Q phosphorylation potential

  7. Other phosphorilated compounds and thioesters also have large free energies of hydrolysis

  8. ATP provides energy by group transfer, not by simple hydrolysis Ranking of biological phosphate compounds by standard free energies of hydrolysis ATP Hydrolysis

  9. ATP donates phosphoryl, pyrophosphoryl, and adenylyl groups

  10. Transphosphorylations between nucleotides occur in all cell types

  11. Biological oxidation-reduction reactions E = E’o + RT/nF ln [acceptor]/[donor] DE’o = E’o (electron acceptor)- E’o (electron donor) DG’o = - nF DE’o

  12. A few types of coenzymes and proteins serve as universal electron carriers Nicotinamide adenine dinucleotide

  13. A few types of coenzymes and proteins serve as universal electron carriers

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