1 / 18

ATP and Energetics of Metabolism

ATP and Energetics of Metabolism. C483 Spring 2013. 1. What is false of a near-equilibrium reaction? A) Concentrations of reactants and products are near equilibrium concentrations. B) The enzyme reaction is most likely not regulated

sharis
Download Presentation

ATP and Energetics of Metabolism

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ATP and Energetics of Metabolism C483 Spring 2013

  2. 1. What is false of a near-equilibrium reaction? A) Concentrations of reactants and products are near equilibrium concentrations. B) The enzyme reaction is most likely not regulated C) The standard free energy of the reaction is near zero. D) The free energy of the reaction is near zero. 2. Which thermodynamic quantity is used to determine if a reaction in a cell is spontaneous? A) △G°' B) △G C) △H D) △S 3. The hydrolysis of ATP to ADP has a △G°' of -30 kJ/mol. If in an E. coli cell the concentrations of ATP, ADP and inorganic phosphate are 7.90 mM, 1.04 mM and 7.9 mM, respectively, which statement is true about the hydrolysis of ATP in the cell? A) Hydrolysis cannot proceed spontaneously. B) The hydrolysis is at equilibrium. C) The free energy of the reaction is less negative than the standard free energy. D) The free energy of the reaction is more negative than the standard free energy. E. More than one of the above are true.

  3. 4. Which of the following is not a factor contributing to the large free energy of hydrolysis of ATP? A) Electrostatic repulsion of oxygen atoms. B) Better solvation of products than ATP itself. C) Complexes with Mg2+ or Mn2+ ions. D) Better stability of products than ATP itself. E) Electrical shielding of products of hydrolysis. 5. ATP is thermodynamically suited as a carrier of phosphoryl groups in animal cells because A) it is stable under cell conditions. B) it is not hydrolyzed in cells without enzyme action. C) it is intermediate in group-transfer potential. D) All of the above.

  4. Catabolism

  5. Anabolism

  6. ATP Hydrolysis • High energy bonds—inherent chemistry • Electrostatic repulsion • Solvation of products • Resonance • Rxn goes to “completion”

  7. Qualitative Predictions • Inherently favorable, unfavorable, or near equilibrium?

  8. Energetics: A metaphor

  9. Standard Free Energy vs. Free Energy DGo’ is negative DG is negative DGo’ is negative DG is zero

  10. Standard Free Energy vs. Free Energy AD DGo’ is -32 kJ DG is -32 kJ ATP ADP + P ADP P DGo’ is -32 kJ DG is zero ATP

  11. Quantitative • Inherent component • Concentration component

  12. Equilibrium • Equilibrium = DEAD! • What is [product]/[rxt] equilibrium of ATP hydrolysis to ADP? • [ADP][Pi]/[ATP] = 4.1 x 105

  13. Free Energy of ATP hydrolysis • Actual cellular concentrations don’t vary much from [Pi]=[ATP] = 5 mmoland [ADP]= 1 mmol • What is the actual free energy of ATP hydrolysis in the cell? More or less than -32 kJ?

  14. Two Types of Reactions • Near-equilibrium reactions • [pdt] and [rxt] near equilibrium concentrations • DG close to zero (regardless of DGo’ ) • Not regulated—part of overall flux of metabolism • Metabolically irreversible reactions • DG far from zero • Can only be overcome by energy input • regulated

  15. ATP in Metabolism • Overcoming a barrier • Can’t change concentrations (ammonia is toxic!) • Couple the reaction to a spontaneous reaction! • Write an equation to couple to ATP hydrolysis:

  16. Mechanism of Coupling

  17. Phosphoryl Transfer in Energetic Intermediates Phosphoryl group transfer potential

  18. Answers • C • B • D • C • D

More Related