08- Metabolism Text

Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsPowerPoint Lectures for Biology, Seventh EditionNeil Campbell and Jane ReeceLectures by Chris RomeroChapter 8n Introduction to !etabolismCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsOverview: The Energy of Life The living cell"Is a miniature factory where thousands of reactions occur "Converts energy in many waysCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsSome organisms "Convert energy to light, as in ioluminescenceFigure 8.1Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsConce!t "#$: %n organism&s metaolism transforms matter and energy, su'ect to the laws of thermodynamicsCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings(etaolism"Is the totality of an organism&s chemical reactions"%rises from interactions etween moleculesCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsOrganization of the Chemistry of Life into Metabolic Pathways% metaolic !athway has many ste!s"That egin with a s!ecific molecule and end with a !roduct"That are each cataly)ed y a s!ecific en)ymeEn)yme $ En)yme * En)yme +AB C D,eaction $ ,eaction * ,eaction +StartingmoleculeProductCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsCataolic !athways"-rea. down com!le/ molecules into sim!ler com!ounds",elease energyCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings%naolic !athways"-uild com!licated molecules from sim!ler ones"Consume energyCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsForms of EnergyEnergy"Is the ca!acity to cause change"E/ists in various forms, of which some can !erform wor.Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings0inetic energy"Is the energy associated with motionPotential energy"Is stored in the location of matter"Includes chemical energy stored in molecular structureCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsEnergy can e converted"1rom one form to anotherOn the !latform, a diverhas more !otential energy#2iving converts !otentialenergy to .inetic energy#Climing u! converts .ineticenergy of muscle movement to !otential energy.In the water, a diver has less !otential energy#Figure 8.2Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Laws of Energy TransformationThermodynamics"Is the study of energy transformationsCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe First Law of Thermodynamics%ccording to the first law of thermodynamics"Energy can e transferred and transformed"Energy cannot e created or destroyedCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings%n e/am!le of energy conversion Figure 8.3 First law of thermodynamics: Energy can e transferred or transformed ut 3either created nor destroyed# 1or e/am!le, the chemical 4!otential5 energy in food will e converted to the .inetic energy of the cheetah&s movement in 45#a!ChemicalenergyCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Second Law of Thermodynamics%ccording to the second law of thermodynamics"S!ontaneous changes that do not re6uire outside energy increase the entro!y, or disorder, of the universeFigure 8.3 "econd law of thermodynamics: Every energy transfer or transformation increasesthe disorder 4entro!y5 of the universe# 1or e/am!le, disorder is added to the cheetah&ssurroundings in the form of heat and the small molecules that are the y7!roductsof metaolism##!$eatco2$2%8Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsBiological Order and isorderLiving systems"Increase the entro!y of the universe"9se energy to maintain order:;lu>lu3C+3C*PiPi8 8,eactants: >lutamic acid and ammoniaProduct 4glutamine5made%2P8PFigure 8.11 Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Regeneration of #TPCataolic !athways"2rive the regeneration of %TP from %2P and !hos!hate%TP synthesisfrom %2P 8P i re6uires energyA4,AD, 6,iEnergy for cellular wor.4endergonic, energy7consuming !rocesses5Energy from cataolism4e/ergonic, energy yielding!rocesses5%TP hydrolysis to %2P 8P i yields energyFigure 8.12 Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsConce!t "#D: En)ymes s!eed u! metaolic reactions y lowering energy arriers% catalyst"Is a chemical agent that s!eeds u! a reaction without eing consumed y the reactionCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings%n en)yme"Is a catalytic !roteinCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe #cti&ation 'arrierEvery chemical reaction etween molecules"Involves oth ond rea.ing and ond formingCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe hydrolysis"Is an e/am!le of a chemical reactionFigure 8.13C*OCCCCCOOCOCOCOO OO OCCC CCCCCC*OC CC*OCOCCC*OCSucraseCOCOOCOCCC*OCCCC*OCCCC*OCCO"ucrose'lucoseFructoseC$*C**O$$CJC$*OJCJC$*OJ8COC CCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings The activation energy, E%"Is the initial amount of energy needed to start a chemical reaction"Is often su!!lied in the form of heat from the surroundings in a systemCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe energy !rofile for an e/ergonic reaction1ree energyProgress of the reaction=G ? OE%Figure 8.1&% -C 2,eactants%C2-Transition state% -C 2ProductsCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings"ow Enzymes Lower the E# 'arrier%n en)yme cataly)es reactions" -y lowering the E% arrierCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe effect of en)ymes on reaction rateProgress of the reactionProductsCourse of reaction without en)yme,eactantsCourse of reaction with en)ymeE%withouten)ymeE% with en)ymeis lower=G is unaffected y en)yme1ree energyFigure 8.1)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsSubstrate S(ecificity of EnzymesThe sustrate"Is the reactant an en)yme acts onThe en)yme"-inds to its sustrate, forming an en)yme7sustrate com!le/Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe active site"Is the region on the en)yme where the sustrate indsFigure 8.1* "u#stateActi(e site-n7ymea!Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsInduced fit of a sustrate"-rings chemical grou!s of the active site into !ositions that enhance their aility to cataly)e the chemical reactionFigure 8.1*#!-n7yme8 su#stratecomple.Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsCatalysis in the Enzyme)s #cti&e SiteIn an en)ymatic reaction"The sustrate inds to the active siteCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe catalytic cycle of an en)yme"u#strates,roducts-n7yme-n7yme8su#stratecomple. 1 Sustrates enter active siteG en)ymechanges sha!e so its active siteemraces the sustrates 4induced fit5# 2Sustrates held inactive site y wea.interactions, such ashydrogen onds andionic onds#3 %ctive site 4and , grou!s ofits amino acids5 can lower E%and s!eed u! a reaction y acting as a tem!late for sustrate orientation, stressing the sustrates and staili)ing the transition state, !roviding a favorale microenvironment, !artici!ating directly in the catalytic reaction#&Sustrates are Converted intoProducts#) Products are,eleased#*%ctive siteIs availale fortwo new sustrate(ole#Figure 8.10Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings The active site can lower an E% arrier y"Orienting sustrates correctly"Straining sustrate onds"Providing a favorale microenvironment"Covalently onding to the sustrateCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsEffects of Local Conitions on Enzyme #cti&ityThe activity of an en)yme"Is affected y general environmental factorsCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsEffects of Temperat're and p(Each en)yme"Cas an o!timal tem!erature in which it can functionFigure 8.18 O!timal tem!erature for en)yme of thermo!hilic,ate of reaction; *; D;"; $;;Tem!erature 4CK5a! %ptimal temperature for two en7ymesO!timal tem!erature forty!ical human en)yme4heat7tolerant5 acteriaCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings"Cas an o!timal !C in which it can functionFigure 8.18 ,ate of reaction#! %ptimal p$ for two en7ymesO!timal !C for !e!sin 4stomach en)yme5O!timal !Cfor try!sin4intestinalen)yme5$; * + D: J F " ICopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsCofactorsCofactors"%re non!rotein en)yme hel!ersCoen)ymes"%re organic cofactorsCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsEn)yme *nhibitorsCom!etitive inhiitors"-ind to the active site of an en)yme, com!eting with the sustrateFigure 8.11#! Competiti(e inhi#ition% com!etitiveinhiitor mimics thesustrate, com!etingfor the active site#Com!etitiveinhiitor% sustrate canind normally to theactive site of anen)yme#Sustrate%ctive siteEn)yme a! 9ormal #indingCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings3oncom!etitive inhiitors"-ind to another !art of an en)yme, changing the functionFigure 8.11 % noncom!etitiveinhiitor inds to theen)yme away fromthe active site, alteringthe conformation ofthe en)yme so that itsactive site no longerfunctions#3oncom!etitive inhiitorc! 9oncompetiti(e inhi#itionCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsConce!t "#:: ,egulation of en)yme activity hel!s control metaolism% cell&s metaolic !athways"(ust e tightly regulatedCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings#llosteric Regulation of Enzymes%llosteric regulation"Is the term used to descrie any case in which a !rotein&s function at one site is affected y inding of a regulatory molecule at another siteCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings+llosteric +cti,ation and *nhibition(any en)ymes are allosterically regulatedCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings"They change sha!e when regulatory molecules ind to s!ecific sites, affecting function"ta#ili7ed inacti(eform%llosteric activaterstaili)es active from%llosteric eny)mewith four suunits%ctive site4one of four5,egulatorysite 4oneof four5Acti(e form%ctivator"ta#ili7ed acti(e form%llosteric activaterstaili)es active formInhiitor:nacti(e form3on7functionalactivesitea! Allosteric acti(ators and inhi#itors. In the cell, activators and inhiitors dissociate when at low concentrations# The en)yme can then oscillate again#OscillationFigure 8.22 Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsCoo!erativity"Is a form of allosteric regulation that can am!lify en)yme activityFigure 8.22 -inding of one sustrate molecule toactive site of one suunit loc.s all suunits in active conformation#Sustrate:nacti(e form "ta#ili7ed acti(e form#! Cooperati(ity: another type of allosteric acti(ation. 3ote that the inactive form shown on the left oscillates ac. and forth with the active form when the active form is not staili)ed y sustrate# Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsFeedbac- *nhibitionIn feedac. inhiition"The end !roduct of a metaolic !athway shuts down the !athwayCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings1eedac. inhiition%ctive siteavailaleIsoleucineused u! ycellFeed#ac3inhi#itionIsoleucine inds to allosteric site%ctive site of en)yme $ no longer inds threonineG!athway is switched offInitial sustrate4threonine5Threoninein active siteEn)yme $4threoninedeaminase5Intermediate %Intermediate -Intermediate CIntermediate 2En)yme *En)yme +En)yme DEn)yme :End !roduct4isoleucine5Figure 8.21Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsS(ecific Localization of Enzymes $ithin the CellAithin the cell, en)ymes may e">rou!ed into com!le/es"Incor!orated into memranesCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings"Contained inside organelles$