Stem-cells：干细胞.ppt

Enzymesn nAll chemical reactions convert All chemical reactions convert reactantsreactants to to productsproducts.Ex.2 Ex.2 HClHCl+Mg +Mg MgCl MgCl2 2+H+H2 2n nEnzymes are a class of Enzymes are a class of proteinprotein.n nThe job of an enzyme is to The job of an enzyme is to catalyze a catalyze a reaction(help it get started)reaction(help it get started).n nEnzymes lower the amount of energy needed to get the reaction going activation energy.Examplesn nDNA polymerase makes DNADNA polymerase makes DNAn nRennin curdles milk proteinRennin curdles milk proteinn nLipase breaks down fatsLipase breaks down fatsn nProtease breaks down proteinsProtease breaks down proteinsn nUsually end with“Usually end with“-asease”How do enzymes work?n nThe material that an enzyme works on is The material that an enzyme works on is called acalled a substrate.substrate.n nEnzymes work like a Enzymes work like a lock and keylock and key must must have right enzyme for each substrate.have right enzyme for each substrate.How do enzymes work?n nThe The active site active site on the enzyme is what on the enzyme is what binds to the substrate.binds to the substrate.Why enzymes?Why enzymes?SpecificnessSpecificness and Reusing enzymes and Reusing enzymesEnzyme Shapen nThe shape of each protein is determined by the The shape of each protein is determined by the sequence sequence of of amino acids amino acids used to make that protein.used to make that protein.n nJust as for proteins,shape is Just as for proteins,shape is extremely importantextremely important.n nIf proteins/enzymes dont have the correct If proteins/enzymes dont have the correct temperaturetemperature,pHpH,or,or salt concentrationsalt concentration,they will,they will lose their shape or lose their shape or denaturedenature and not be able to and not be able to function.function.DenaturingDenaturinghttp:/www.lewport.wnyric.org/jwanamaker/animations/Enzyme%20activity.htmlTutorial activityCompetitive Inhibitionn nIn a process called In a process called competitivecompetitive inhibitioninhibition,molecules that fit the active,molecules that fit the active site can prevent the enzyme from site can prevent the enzyme from working.working.