lecture0222final_1

lecture0222final_1 - Thermodynamics vs. kinetics...

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Thermodynamics vs. kinetics Calculation of ΔG will tell us  whether a reaction  can  occur under  the prevailing conditions and how  much useful energy it will release. ΔG o can be used to calculate the   equilibrium constant, K eq  and hence  the [products] and [reactants] at  equilibrium . But neither tell us anything about  how  fast   a reaction occurs in a cell
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Kinetics and Activation energy   Most reactions with negative ΔG  do not occur with any significant  rate in cells unless they are  catalyzed by an enzyme.   This is because most of the reactant  molecules do not have enough  thermal or kinetic energy to  overcome a barrier for reaction  called the a A ctivation energy   E a
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Figure 3.8
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Figure 3.9
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Enzymes  Enzymes, as catalysts lower E a Enzymes do not alter ΔG –  They cannot make a reaction occur  spontaneously if it is  thermodynamically unfavourable. They cannot alter the concentrations of  reactants and products in a reaction  mixture that is at equilibrium They cannot extract more useful  energy per mole of reactants – they  can only extract it faster!
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Enzymes  As a catalyst, an enzyme also …. . is only required in small amounts
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This note was uploaded on 05/11/2010 for the course BIOLOGY 105 taught by Professor Richard during the Spring '10 term at George Mason.

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lecture0222final_1 - Thermodynamics vs. kinetics...

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