lecture 8_notes

lecture 8_notes - • Enzymes are biological catalysts with...

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Lecture 8 Review of chemical reactions How do we know if a reaction will take place? Compare G of products and reagents G° is for standard amounts G is for specific amounts, and thus applies to a given condition G = G° + RT lnK K is the [products]/[reagents] ratio equilibrium is reached when G = 0 thus, 0 = G° + RT lnK and G° = - RT lnK therefore, if you know K of equilibrium, you can derive also, the sign of G depends on K conclusion, reactions can flow from products to reagents when the ratio P/R reaches a certain value. This threshold value depends on Enzymes Rx may have a large neg DG but still not proceed at any measurable rate (e.g. burning of sugar) Energy barrier requires activation energy (stretching of bonds, or other small change) Catalysts increase the rate of reaction by diminishing the activation energy
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Unformatted text preview: • Enzymes are biological catalysts with high specificity • Origins • Ribozymes (RNA) • Proteins • Terms • Substrate -- Product (but, keep in mind equilibrium constant) • Active site • Enzyme-Substrate complex • E + S -> ES -> E + P • Free energy graph • Important enzyme facts: do not change equilibrium, do not change DG, change Energy of ac-tivation, speed reactions, equilibrium and reverse reaction still apply! • Substrate concentration affects reaction rate: graph rate by conc • Regulation of enzyme action • Allosteric enzyme respond to stimulus other than substrate by changing shape • Inactive + activator --> Active • Active + inhibitor --> Inactive • Example: Thr -> alphaKbut -> -> -> -> Ile • Ile inhibits first step...
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This note was uploaded on 06/07/2009 for the course BIS BIS2A taught by Professor Lucacomai during the Spring '09 term at UC Davis.

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