BiochemFall2017_Lecture11.pdf - Lecture 11 Chapters 11...

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Lecture 11: Chapters 11 Introduction to Enzymatic Catalysis
Lecture11 Outline: Text Book: Chapter 11 (Pages 410 - 421 ) My New Open Office Hour: Every Friday 2:30 pm to 3:30 pm Location: Silver 1002, Section A – Review of Chemical Catalysis – Enzymes as Biological Catalysts – Energetic Basis of Enzyme Catalysis – Enzyme Substrate Interactions
Simple irreversible first-order reaction: A → B Reaction follows the equation [A] t = [A] o e -kt • A first-order rate constant has units of (time) - 1 , whereas a second-order rate constant has units of (concentration) -1 (time) -1 Half-life ( t 1/2 ): Time taken for reactant concentration to be halved ln[A] versus t gives linear plot: slope of this line (d ln[A]/d t ) is equal to - k 1 Complex multistep reaction schemes can be simplified by recognition of rate-limiting step : slowest step in a multistep process rate-limiting step determines the experimentally observed rate for the entire process Simple Chemical Reactions: Review
Barriers to chemical reactions occur because a reactant molecule must pass through a high-energy state to form products Transition state : Highest energy point along the reaction coordinate This free energy barrier is called the activation energy Transition States of Chemical Conversions A reasonable path for the transition of a pyranose (such as glucose) from boat (1) to chair (3) conformation. The highest energy state—the transition state—will look something like (2).
Effect of a Catalyst on Activation energy 11 - 5 Catalyst lowers standard free energy of activation , G o‡ : accelerates reaction rate

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