Class8_glycolysiskinetics.pptx - For, after all, how do we...

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“For, after all, how do we know that two and two make four? Or that theforce of gravity works? Or that the past is unchangeable? If both the pastand the external world exist only in the mind, and if the mind itself iscontrollable – what then?”- George Orwell, 1984“Any technological advance can be dangerous. Fire was dangerous fromthe start, and so (even more so) was speech - and both are stilldangerous to this day - but human beings would not be human withoutthem.”IsaacAsimov
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The reaction quotient Q, gives the currentstate of the products and reactantsFor the reaction A+B ↔ C+D,Q=[C][D]/[A][B] is thereaction quotient.The instantaneous Gibbs energy for a reaction isgiven by ΔG= Δ+ RT lnQ or 1.4 log QIfQ < Keq: The reaction will shift to the right (i.e.ΔG<0,reactiongoes in the forward direction, and thus more products will form)IfQ > Keq: The reaction will shift to the left (i.e.ΔG>0,reaction goesin the reverse direction, and thus more reactants will form)IfQ = Keq: The reaction is at equilibriumG=0)Zumdahl, Steven; Zumdahl, Susan (2003).Chemistry 6th Edition.Houghton Mifflin Company.ISBN 0-618-22158-1.
Clicker question: For the reaction A+B ↔ C+D, ifG ispositive, how would the products or reactants have tochange Q to makeG negative?GG
Energetically unfavorable reactions are enabled bycouplingthem with favorable reactionsExample: Glutamic acid + NH3 ↔ glutamine, ΔG°’ = +3.4 kcal/molRecall that ΔG°’ for ATP hydrolysis = -7.3 kcal/molFirst, areaction intermediateis formed in the reactionGlutamic acid + ATP ↔ glutamyl phosphate + ADPSecond, it is energetically favorable for the reaction intermediate toproceed to replace its phosphate with an amine group (NH3) in thereaction Glutamyl phosphate ↔ glutamine + PiTotal reaction is glutamic acid + ATP + NH3 ↔ glutamine + ADP + Pi
Thedifference in ΔG°,not the absolute value ofΔG°, will determine the ΔG of a coupled reactionAnything higher on thechart, (larger ΔG°),candrive the reversereactionof anythinglower on the chartFor example, hydrolysisof phosphoenolpyruvatecan drive ATP synthesis,and ATP hydrolysis candrive phosphorylation ofglucose
Clicker question. Based on the chart, what is theapproximateG°’ for the reaction Glucose -->

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Glycolysis, RNA, Enzyme, Reaction, Catalysis, 1984, Clicker question

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