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Chp.14 Principles of Bioenergetics

Chp.14 Principles of Bioenergetics. Metabolism = the sum of all chemical reactions that take place in a cell or organism. Bioenergetics = the quantitative study of the energy transductions that occur in

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Chp.14 Principles of Bioenergetics

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  1. Chp.14 Principles of Bioenergetics Metabolism = the sum of all chemical reactions that take place in a cell or organism. Bioenergetics = the quantitative study of the energy transductions that occur in in living cells and the nature and function of the chemical processes underlying these transductions.

  2. 4 x 10 11 metric tons of carbon are turned over in the biosphere each year.

  3. Catabolic pathways generally converge. Anabolic pathways diverge Some pathways are cyclic.

  4. A Metabolic “Map” Acetyl-CoA plays central role Voet & Voet Fig. 15-1

  5. Acetyl-Coenzyme A Fig 3-6 Page 57

  6. Glycolysis -> Citric Acid Cycle -> Oxidative Phosphorylation Oxidation of glucose 24 electrons Glucose + 6O2 6CO2 + 6H2O DG’o = -686 kcal/mole A fraction of this free energy will be harvested as chemical energy in the form of ATP

  7. Biological Systems Obey the Physical Laws of Thermodynamics DG = DH - TDS DH = DU + PDV G = Gibbs Free Energy H = Enthalpy S = Entropy U = Internal Energy

  8. First Law of Thermodydamics - The Principle of Conservation of Energy For any physical or chemical change, the total amount of energy in the universe remains constant; energy may change form as it is transported from one region to another, but it cannot be created or destroyed.

  9. Living systems can couple energy requiring reactions to those which are spontaneous (exergonic)

  10. A chemical example of reaction coupling

  11. The Second Law of Thermodynamics In all natural processes, the entropy of the universe increases. The oxidation of glucose results in a significant increase in entropy.

  12. Free Energy Calculations: DG < 0, product formation is favored DG = 0, reaction at equilibrium DG > 0, substrate formation favored At equilibrium, If all [i] = 1 M,

  13. Adenosine triphosphate (ATP)

  14. Why is ATP a “high-energy” compound ?

  15. ATP is kinetically very stable ATP + H2O Slow reaction ADP + HPO42- Garrett & Grisham Fig. 3.8 ATP in water is not readily converted to ADP, but needs enzymes to mediate hydrolysis.

  16. ATP the universal energy carrier. It releases a significant amount of free energy upon hydrolysis. But not too much so it can be a conduit between “high energy” phosphate donors and low energy acceptors.

  17. Why are the hydrolysis products (ADP+Pi) more stable than the reactants (ATP)? (1) More resonance forms per phosphate in hydrolysis products ATP ADP Pi (2) Charge separation in products (3) Better solvation of products

  18. Creatine.

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