Bio240%20lectJan22

Bio240%20lectJan22 - Enzyme kinetics V= Vmax[S[S Km Enzyme...

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1 V max [S] [S] + K m V = Enzyme kinetics Increased blood flow cGMP Phosphodiesterase Viagra Target Drug HIV protease Ritonavir HIV reverse transcriptase AZT Dihydrofolate reductase Methotrexate Glycopeptide transpeptidase Penicillin Prostaglandin synthase Aspirin Enzyme Inhibitors
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2 Non-competitive inhibitors bind to enzyme sites that are non-substrate binding sites K m is unaltered, V max decreases The K m increases, V max stays the same Competitive inhibitors bind to the enzymes active site competing with substrate Competitive Inhibitor Non-competitive Inhibitor Allostery When a small molecule acts as an effector or regulator to activate or inactivate an action of an enzyme, the enzyme is said to be under allosteric control. The binding of the small ligand is distant from the enzyme’s active site and regulation is a result of a conformational change in the enzyme when the ligand is bound
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3 Effects of different enzyme regulation on chemical reactions _ If E can down-regulate enz 2 - end-product inhibition Multiple enzymes participate in reaction pathways
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4 Alosteric modulation depends on levels of the modulator ATP AMP Positive Feedback + Citrate Negative Feedback _ Enzymes often have mutiple allosteric regulators
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5 Summary - Enzymes are protein catalysts that lower activation energy - Substrates bind to the active site of enzymes, causing conformational changes that result in catalytic activity - Velocity of enzyme-catalyzed reactions depends on 1) [E] 2) Enzyme catalytic efficiency, K cat 3) Enzyme/substrate affinity, K m -Maximum reaction velocity V max depends on 1) and 2), where as 3) affects reaction velocity only at subsaturating substrate levels. -Multi-subunit enzymes having multiple active sites exhibit copperativity. Allosteric modulators can cuase cooperativity by binding to non-substrate, regulatory sites - Enzymes accelerate reaction towards equilibrium - Isozymes provide diversity of expression and enzyme properties Topic: Transport of solutes and water -Modes of transport -passive solute transport -Facilitated diffusion -Active transport (primary and secondary) -Modulation of channels and transporters -Osmosis
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6 Transport across cell membranes Despite having similar sum totals of solutes ( dissolved matter ) inside and outside a cell, solute composition is very different [K + ] in > [K + ] out [Na + ] in < [Na + ] out How is this concentration gradient maintained? How is the blood plasma composition maintained in fresh water fish?
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7 What mechanisms exist to transport hydrophilic sugars from a hummingbird’s intestinal lumen across epethlial membranes into its blood? Humming birds are dietary specialists ingesting sugary nectar Simple diffusion viewed macroscopically and microscopically If a membrane is selectively glucose permeable , glucose will pass through by random motion until equilibrium is reached: ie brought to a stable state in which no futher change is possible without input or output of energy) Here equilibrium would be reached when [glucose] on either side is equal Passive transport occurs by simple diffusion
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This note was uploaded on 04/29/2008 for the course BIOS 240 taught by Professor Richmond&warphea during the Spring '08 term at Ill. Chicago.

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Bio240%20lectJan22 - Enzyme kinetics V= Vmax[S[S Km Enzyme...

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