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Bioenergetics

Bioenergetics. Uses of energy. Synthetic work Concentration work Mechanical work Electrical work Heat production Bioluminescence. Where does the energy come from?. Sun—common Phototrophs Chemotrophs Geothermal sources—rare Chemotrophs. Where does the energy go?.

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Bioenergetics

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  1. Bioenergetics

  2. Uses of energy • Synthetic work • Concentration work • Mechanical work • Electrical work • Heat production • Bioluminescence

  3. Where does the energy come from? • Sun—common • Phototrophs • Chemotrophs • Geothermal sources—rare • Chemotrophs

  4. Where does the energy go?

  5. Thermodynamics: energy and energy flow Bioenergics: thermodynamics of living things

  6. Thermodynamic terms • System—what we're looking out • Surroundings—everything else • Open system—exchanges between system and surroundings • Closed system • State—the physical properties of the system, e.g. temp, pressure, conc. etc. • Work—use of energy to do something (except produce heat)

  7. First Law of Thermodynamics Energy can change forms, but can neither be created nor destroyed

  8. Internal energy (E) Or, for a chemical reaction:

  9. Enthalpy (H)heat content But DV for biological (aqueous) systems is zero, so DHDE

  10. Change in enthalpy is easily measured DH > 0: endothermic DH < 0: exothermic

  11. Usefulness of DH DH is a "state function", determined by change in state, not pathway between states DH = -673 kcal/mol True in either a calorimeter (easily measured) or a cell (very hard to measure)

  12. Not all processes occur • Can't be explained just by 1st law

  13. Second law of thermodynamics • The universe always tends toward greater disorder • Entropy (S) is measure of disorder

  14. Gibb's free energy Combines both enthalpy (H) and entropy (S) and thus combines 1st and 2nd laws of thermodynamics At constant temperature, volume, and pressure

  15. Thermodynamic spontaneity

  16. Spontaneous means a reaction CAN happen, not that it WILL • G is state function: pathway independent • Rate of a reaction: pathway dependent • kinetics DG = -686 kcal/mol

  17. Reversible Reactions

  18. Keq and G Std. Conditions: 25 C, 1 M conc., 1 atm., pH 7.0

  19. G's are additive

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