F BICH 410 1st Edition Lecture 3 Outline of Last Lecture Ka pKa pH Buffers Biosystems Thermodynamics Outline of Current Lecture Enthalpy H Entropy S Free Energy G Enthalpy most biosystems operate under constant pressure o H E PV o Delta H q o deltaE q PdeltaV o delta H approximated as heat absorbed Enthalpic Reactions o Exothermic delta H 0 Endothermic delta H 0 0 Van T Hoff plot deltaH R d lnKeq d 1 T o Slope is deltaH0 o Enthalpy change determined from temp dependence of equilibrium constant Thermodynamic standard state one defined set of conditions o Typ 1M reactants and products at a temp 298K or in biosystems 31 o Standard state denoted by superscript not o Delta G0 standard free energy change Biological standard states assume conc of 1M o Biochemical reactions buffered so H doesn t change o Conc of water is soln is high 55 5M so conc of water stays the same therefore water and H value bother use value of 1 o deltaGo says to ignore H and water conc Entropy measure of disorder o 2nd law entropy of system and surroundings always increases o deltaS final state more ordered not favorable direction o deltaS final stae less complex more disordered favorable Neither deltaH or deltaS alone sufficient to determine spontaneity deltaG deltaH TdeltaS H total energy S wasted energy G useful energy Delta G tells direction of reaction These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Once rxn is at equilibrium no work can be done deltaG equilibrium 0 If deltaG 0 deltaS deltaH T o Entropic and enthalpic changes are equal If delta g 0 exergonic rxn and energy released If delta G 0 endergonic rxn and energy absorbed Delta G is ratio of equilibrium and nonequilibrium initial conc of products and reactants o Delta G RTln Peq Req Pi Ri RTln Keq PiRi Free energy change is how far from equilibrium rxn is Under standard conditions initial conc are 1 pi ri therefore deltaG0 RTlnKeq deltaG0 0 Keq 1 therefore there will be more reactants rxn will move left deltaG0 0 Keq 1 therefore there will be more products rxn will move to right Keq Peq Req important eqns o DelatG DeltaG0 RTln P R o DeltaG DeltaH TdeltaS Use if given initial cellular conc o DeltaG0 RTlnKeq deltaH 0 deltaS 0 deltaG 0 deltaH 0 deltaS 0 deltaG 0 Thermodynamic State Functions are additive o Applied to standard and nonstantard states o Free energy of two consecutive rxns add Molar vs millimolar which to use o Doesn t matter bc units cancel out if equal number of products and reactants o If more P than R must convert to M
View Full Document
Unlocking...