chapter 8 lecture notes

This phenomenon is called induced fit induced fit

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Unformatted text preview: would it be inappropriate to speed up these reac1ons by applying heat? Key Points: * However enzymes do not: 1. Change the ΔG 2. Turn an endergonic reac,on into an exergonic reac,on Substrate Specificity of Enzymes Substrates: reactants that enzymes act on Enzyme + Substrate Enzyme  ­Substrate Complex Sucrase + Sucrose + H2O Sucrase –Sucrose ­H20 Complex A reac,on catalyzes by an enzyme is very specific * Example: Sucrase is specific for sucrose Why are enzymes able to recognize molecular differences? Enzyme + Product Sucrase + Glucose + Fructose not maltose Ac1ve Site: where an enzyme binds to its substrate Glucose Pocket or Grove Induced Fit Hexokinase Hexokinase ­Glucose Complex Ac,ve site contains only a few AA Rest of the protein molecule provides the frame work that determines the configura,on of the ac,ve site * This interac,on causes the enzyme to change shape slightly so the ac,ve site fits more snuggly around the substrate. This phenomenon is called Induced Fit Induced Fit Cataly1c cycle of an enzyme Substrates bind to enzyme at ac,ve site  ­ “Induce Fit” Substrates are held in ac,ve site by weak interac,ons – such as ionic bonds , hydrogen bonds, hydrophobic interac,ons New Shape * Ac,ve site is available for two new substrates Substrates are converted to products Key Points: Small amounts of enzymes can have a huge metabolic impact by func,oning over and over again in cataly,c cycles Most metabolic reac1ons are reversible Enzymes can catalyze both forward and reverse reac,ons  ­ depends on which direc,on has a –ΔG. * Net effect is always the direc,on of equilibrium Enzymes use specific mechanisms to lower the ac1va1on energy and speed up a reac1on Ac,ve Site Examples of some mechanisms that take place in the acIve site: 1. 2.  Ac,ve site stress th...
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