BIBC 102: Metabolic Biochemistry (Prof. Scheffler)TA: Edward Chen [email protected]: Mondays 4-5pm @ CLICSHandout #1I. Enzymea. Function- Enzyme is a catalyst that speeds up rate of reaction by lowering activation energy.b. Classification (LNC p. 192)c. Specificity- Enzymes are very selective.- Two models for formation of enzyme-substrate complex:1. Lock and key model (lock = enzyme, key = substrate)2. Induced fit (conformation change at active site where the enzyme changes)d. Thermodynamics- General Reaction: E + S ES EP E + Pa. Enzymes do nothing to ∆G. They only affect ∆G≠b. Enzymes alter the activation energy by stabilizing the transition state.e. Kinetics- 1st order rxns:[A] = [Ao]e-kt or ln [A] = ln [Ao] x -ktReaction Rates: aA + bB → cC + dDKeq = [P]/[S] = [C]c[D]d / [A]a[B]band ∆G‘o = -RT ln Keq(if k > 1, ∆G < 0 → rxn forward)(if k < 1, ∆G > 0 → rxn backwards)When k = 0 → equilibriumm = -kln [Ao]BIBC 102: Metabolic Biochemistry (Prof. Scheffler)TA: Edward Chen [email protected]: Mondays 4-5pm @ CLICS- 2nd order rxns:1/[A] = 1/ [Ao] + ktRegulation of Enzyme Activity- At the level of gene expression and protein turnovero Ex: - By covalent modifications of side chainso Ex: - By binding of small molecules (ligands) that are not substrateso Ex: II. General Reaction:E + S 11kk -�������� ES 22kk -�������� E + P- Two Assumptions of Michaelis–Menten:- Michaelis-Menten Equation:Vo = [ ]d ESdtmax[ ][ ]mV SK S+ ; where Km = 2 11k kk-+1/[A]BIBC 102: Metabolic Biochemistry (Prof. Scheffler)TA: Edward Chen [email protected]: Mondays 4-5pm @ CLICS- Lineweaver-Burk equation: (AKA double reciprocal plot)max1V1oV = maxmKV� 1[ ]S + max1V- Reactions with more than one substrate and enzyme inhibition:(a) Enzyme reaction involving a ternary complexBIBC 102: Metabolic Biochemistry (Prof. Scheffler)TA: Edward Chen [email protected]: Mondays 4-5pm @ CLICS(b) Enzyme reaction in which no ternary complex is formedIII. Enzyme Inhibitors:- Competitive Inhibition:BIBC 102: Metabolic Biochemistry (Prof. Scheffler)TA: Edward Chen [email protected]: Mondays 4-5pm @ CLICS- Non-competitive Inhibition:- Mixed Inhibition:Equation:Graph:BIBC 102: Metabolic Biochemistry (Prof. Scheffler)TA: Edward Chen [email protected]: Mondays 4-5pm @ CLICSIV. Regulation- Allosteric RegulationAllosteric inhibitor (-) = binds to site and decreases activity of the enzyme.Allosteric activator (+) = blah blah and increases blah blah =p- Inhibitiono Feedback –o Reversible inhibition –o Irreversible inhibition –o Allosteric enzyme conformation change –V. Types of Organic Reactions1) Group transfer2) Oxidation-reduction reactions3) Eliminations, isomerizations, rearrangements4) making or breaking of C-C bondsSee slide 3-39 for detailsVI. Bioenergetics- Gibbs Free Energy: ∆G = ∆H - T∆S(1) Gibbs Free Energy (∆G) – the change in energy between the product and the substrate.(2) Enthalpy (∆H) – the change of heat content in a reacting system.(3) Entropy (∆S) – measurement of disorder.- Coupling Reactions(1) endergonic: need energy(2) exergonic: release energy(3) Use coupling to drive reactionsBIBC 102: Metabolic Biochemistry (Prof. Scheffler)TA: Edward Chen [email protected]: Mondays 4-5pm @ CLICSWHAT’S THIS? SOMETHING TO
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