MCB 450 1st Edition Lecture 10Outline of Last Lecture I. Membrane Proteinsa. peripheralb. integralc. lipid-anchoredII. Membrane TransportOutline of Current Lecture I. Principles of Enzyme Catalysisa. Free Energy and Equilibriab. Keq and ΔG in Living Cellsc. Activation Energyd. Enzyme-Substrate InteractionCurrent LectureChemical reactions in cells-In a living cell, thousands of reaction have to go on~107 fold rate enhancement by carbonic anhydrase-One of the fastest enzymes knownoVery important in our physiologyRate enhancements by enzymes-Don't have to know all of these rates and rate enhancements by emphasizes a number of different pointsMore about enzymes-Activity of enzymes can be turned up or turned down as neededClasses of enzymes-Enzymes have classification numbers oE.g. trypsin 2.4.21.4, chymotrypsin 3.4.21.1-Exam questions may have to do with recognizing a reaction and labeling itEnzyme cofactors-Not required to memorize the list of enzyme cofactors at this pointSome thermodynamic considerations-Two different thermodynamic properties that we must consideroDelta-G -- free energy changeoThe free energyPredicting spontaneity of a reaction from delta-GThese 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.-Reaction is written to be reversible-Have to define in which direction you are going with the reactionProgress curve for an exergonic reaction-Exergonic reaction -- release energyoWill proceed spontaneouslyProgress curve for endergonic reaction-Endergonic reaction -- input of energy neededoWill not proceed spontaneously-Delta-G indicates whether the reaction will be spontaneous or not but will not tell us anything about the rate of the reactionMore thermodynamic considerations-Want to relate delta-G to the equilibrium constantHow do we measure free energy change (delta-G)?-You'll be given the value of R on the exam-R -- the gas constantBiochemical standard free energy change-Delta-G zero prime is more realistic in its use in biochemistryRelation between delta-G zero prime and K'eq-Product formation favored-Talking about the standard free energy under a set of standardized conditionsActual concentrations of A & B can modify delta-G in living cells-Under "non-equilibrium" conditions-In a living cell it is normally away from equilibrium or at "non-equilibrium"Enzymes accelerate the reaction rate but do not affect the position of the equilibrium-Enzyme allows the reaction to reach equilibrium much fasterEnzymes facilitate formation of the transition state-Transition state - least stable intermediate in the reactionConcepts-Know definitions:oActive siteoEnzyme-substrate complexoBinding energy-Binding energy -- key to lowering activation energyActive site amino acids may include amino acids that are widely separate in the 1 sequence-Shows N to C terminus-Makes a point that side chains tend to be positioned on the loopsLock-and-key model of substrate binding-Aren't a rigid lock and key arrangement-The active site will change shapesEnzymes are complementary to transition state, not substrate-Metal stick analogy-Groups that will interact with the substrate are shown in redEnzymes are complementary to transition state-Can we use this to develop
View Full Document