enzyme_mechanism_with_notes

enzyme_mechanism_with_notes - Enzymes Enzymes An enzyme is...

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nzymes Enzymes
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• An enzyme is a protein or RNA based catalyst for biochemical reactions • Most, if not all metabolic pathways are regulated by regulating enzyme function. nzymes catalyze reactions under mild • Enzymes catalyze reactions under mild conditions. • Not much happens in cells without them
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nzymes work because they bind specific Enzymes work because they bind specific substrates with high fidelity. • A single amino acid chain folds up into a specific structure that then regulates the function of a cell. Pretty cool!
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There are many types of enzymes
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What is a catalyst? increased rate of reaction activation energy is reduced Δ G o is NOT changed G cat catalyst is not consumed by the action G 0’ reaction
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referential binding of the transition state preferential binding of the transition state
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hat does a catalyst do? What does a catalyst do? Comparison of reaction rates with and without catalysis
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ow does an enzyme do that? How does an enzyme do that? •E n z ymes bind one or more substrate molecules with high specificity • Stereo isomer and geometric isomers are selected ocalize required cofactors in reactions Localize required cofactors in reactions hange enthalpy of activation Change enthalpy of activation • Change entropy of activation
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reaction rates up to 10 8 x the ncatalyzed reaction uncatalyzed reaction enzymes are protein structures with “active sites” for binding “substrates” binding of substrate to active site initiates catalysis inding site is binding site is complementary to substrate structure
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high specificity for substrates enzymes recognize stereoisomersand geometric isomers
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se of amino acid side chains for acid ase use of amino acid side chains for acid-base catalysis, and cofactors binding energy from the bonds made etween substrate and enzyme in the active between substrate and enzyme in the active site entropy reduction: bringing substrates together in the correct orientation desolvation of substrates: water solvation is replaced by amino acid side chains
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Models of Enzyme substrate interactions ock and key: DHFR Lock and key: DHFR • Substrates bind to preformed active site
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Models of Enzyme substrate interactions duced fit: Hexose kinase This prevents the Induced fit: Hexose kinase transfer of P to H2O at active site. Xylose binds and cause conformational change but P is g transferred to water not the sugar. • Binding of hexose causes conformational change that allows active site to form.
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Transition State Theory • Slow reactions face significant activation arriers that must be surmounted during the barriers that must be surmounted during the reaction –transition state theory is applicable for catalysis te constants and free energies can be –rate constants and free energies can be related k k B T h exp  G RT
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Rate Acceleration • The enzyme lowers the activation barrier
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enzyme_mechanism_with_notes - Enzymes Enzymes An enzyme is...

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