lecture8 - Free Energy and Change Free A spontaneous...

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Free Energy and Change Free Energy and Change A spontaneous process: A spontaneous process: one that takes place with no outside influence note that “spontaneous” carries no indication of rate relates to thermodynamics, not kinetics The most useful criterion for predicting spontaneity is the change in Gibbs free energy change in Gibbs free energy, G, G, for a process G < 0 exergonic, spontaneous, energy released G = 0 the system is at equilibrium G > 0 endergonic, non-spontaneous, energy
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G°’ G°’ Consider the hydrolysis of ATP because G°’ < 0, this process is spontaneous and energy is released G¡' =  - (8.31 x 10 -3  kJ¥mol -1 ) (298 K)  ln 2.23 x 10 5  =  -30.5 kJ¥mol -1  = -7.29 kcal mol -1 ATP +  H 2 O ADP +  P +  H + K' eq   = [ADP] [P i ] [H + ] [ATP] at pH 7.0 and 25¡C
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Thermodynamics and Life Thermodynamics and Life Question: is the existence of living things a violation of the laws of thermodynamics? Free energy, G, for a substance defined in terms of its enthalpy (H), entropy (S), and temperature (T) at constant pressure we are interested in changes in free energy for biochemical transformations H is the heat of reaction at constant pressure G = H - TS G = DH - TDS
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Nature of Metabolism Metabolism: Metabolism: the chemical reactions of biomolecules, consists of both catabolism and anabolism catabolism catabolism : the breakdown of larger molecules into smaller ones; an oxidative process that releases energy (can be coupled to ATP production) anabolism anabolism : the synthesis of larger molecules from smaller ones; a reductive process that requires energy oxidation oxidation : the loss of electrons; the substance that donates the electrons is called a reducing agent reducing agent reduction reduction
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lecture8 - Free Energy and Change Free A spontaneous...

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