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Energy Flow Through Cells

Dive into the intricate world of cell energy flow and bioenergetics, exploring concepts like entropy, thermodynamics laws, and free energy to understand how cells require, store, and utilize energy. Learn about ΔG, equilibrium constants, and why cellular reactions never reach true equilibrium.

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Energy Flow Through Cells

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  1. Energy Flow Through Cells

  2. Energy • What are some of the reasons that cells require energy?

  3. Energy • From where do organisms get the energy they need?

  4. Bioenergetics • What is the difference between and open and a closed system from the standpoint of energy? What kind of a system is a cell?

  5. Bioenergetics • What is the unit used to measure energy changes in cells? • How do we define this unit?

  6. Bioenergetics • What does the first law of thermodynamics say? • What do we mean by the internal energy of a system? energy stored = energy in – energy out

  7. Bioenergetics • What is enthalpy and how is it related to internal energy? H = E + PV or ΔH = ΔE + ΔPV What happens to ΔH in an exothermic reaction? an endothermic reaction?

  8. Bioenergetics • What does the second law of thermodynamics tell us? • For what purpose do cell biologist make use of this law?

  9. Bioenergetics • What is the relationship between entropy and thermodynamic spontaneity? • How can the order within a cell or the entropy of a reaction decrease?

  10. Bioenergetics • To determine whether a particular reaction will take place in a cell we use the concept of free energy. • What is the relationship between the change in free energy, enthapy and entropy? ΔG = ΔH - TΔS

  11. Bioenergetics

  12. Bioenergetics • How can we determine from the value of ΔG whether a reaction will occur spontaneously? • What enables us to characterize reactions as endergonic or exergonic?

  13. Bioenergetics

  14. Bioenergetics • How can we use the equilibrium constant to determine whether a reaction can occur in a specific direction? Keq = [product]eq/[reactant]eq for glucose-6-PO4 fructose-6-PO4 Keq = [fructose-6-PO4]eq/[glucose-6-PO4]eq = 0.5

  15. Bioenergetics • reactions proceed toward equilibrium

  16. Bioenergetics • How do we actually calculate ΔG? aA + bB cC + dD ΔG = -RTlnKeq + RT ln [C]c[D]d/[A]a[B]b R = 1.987 cal/mol-oK T at 25oC = 298oK

  17. Bioenergetics • What is the difference between ΔG’ and ΔGo’? • How does this affect the actual calculation? since ΔGo’ = - RT ln K’eq ΔG’ = ΔGo’ + 592 ln [C]c[D]d/[A]a[B]b

  18. Bioenergetics

  19. Bioenergetics • How does the cell biologist use the value of ΔG’ ?

  20. Bioenergetics • Why do cellular reactions never reach equilibrium? • What is the steady state and how is it maintained?

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