Chapter 6

Chapter 6 - Chapter 6: The Behavior of Proteins Enzymes 1....

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Chapter 6: The Behavior of Proteins – Enzymes 1. Enzymes Are Effective Biological Catalysts a. Catalysis is the most important function of proteins b. Enzymes are the mot efficient catalysts – can increase the rate of a rxn by 10 20 X c. Have extremely high specificity d. Globular 2. Kinetics vs. Thermodynamics a. Thermodynamics – Spontaneity & Standard Free Energy: ΔG o i. ΔG o is the difference between the energies of the reactants (the initial state) and the energies of the produces (final state) of a reaction. ii. The question of whether or not a reaction is favored is based on ΔG o iii. Spontaneous does not mean instantaneous b. Kinetics – The Rate of a Reaction i. The rate of a reaction depends on activation energy 1. The activation energy is the amount of free energy required to bring the reactants to the transition state 2. The presence of an enzyme lowers the activation energy needed for substrate molecules to reach the transition state 3. Enzyme Kinetic Equations a. The rate of a chemical reaction is expressed in terms of a change in the concentration of a reactant or a product in a given time interval b. The rates of appearance of product and disappearance of reactant are stoichemetrically equal i. A + B P 1. = - [ ] =- [ ] = [ ] Rate ∆ A ∆t ∆ B ∆t ∆ P ∆t 2. Rate = k[A] f [B] g a. The order of the reaction is the sum of the exponent values c. Zero Order Reactions only depend on rate constant k.
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d. The rate constant, k, and the exponents must be measured experimentally for each reaction 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 4. Enzyme – Substrate Binding a. A substrate binds, usually by noncovalent interactions, to the active site of the enzyme, frequently located in a cleft consisting of certain amino acids that are essential for enzymatic activity b. Induced-fit model i. The binding of a substrate induces a conformational change in the enzyme that results in a
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This note was uploaded on 03/22/2009 for the course CHEM 430 taught by Professor Redinbo during the Spring '07 term at UNC.

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Chapter 6 - Chapter 6: The Behavior of Proteins Enzymes 1....

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