FBICH 410 1st Edition Lecture 3Outline of Last Lecture - Ka, pKa, pH- Buffers & Biosystems- ThermodynamicsOutline of Current Lecture - Enthalpy (H) Entropy (S) Free Energy (G)- Enthalpy most biosystems operate under constant pressureo H=E+PV o Delta H=qo deltaE=q-PdeltaVo delta H approximated as heat absorbed- Enthalpic Reactionso Exothermic: delta H<0 Endothermic: delta H>0- Van’T Hoff plot- deltaH0=-R(d(lnKeq)/d(1/T))o Slope is deltaH0o Enthalpy change determined from temp dependence of equilibrium constant- Thermodynamic standard state- one defined set of conditionso Typ. 1M reactants and products at a temp (298K) or in biosystems (31)o Standard state denoted by superscript noto Delta G0=standard free energy change- Biological standard states assume conc of 1Mo Biochemical reactions buffered so [H+] doesn’t changeo 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 1o 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 directiono 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 reactionThese 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/To 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 reactantso 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 eqnso DelatG=DeltaG0+RTln[P]/[R] o DeltaG=DeltaH-TdeltaS Use if given initial/cellular conco DeltaG0=-RTlnKeq- deltaH<0 deltaS>0 deltaG<0- deltaH>0 deltaS<0 deltaG>0- Thermodynamic State Functions are additiveo Applied to standard and nonstantard stateso 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 reactantso If more P than R must convert to
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