SM_c14GlycolysisGluconeogenesisandthePentosePhosphatePathway

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1、c14GlycolysisGluconeogenesisandthePentosePhosphatePathway.qxd12/6/124:34PMPageS-160chapterGlycolysis,Gluconeogenesis,and14thePentosePhosphatePathway1.EquationforthePreparatoryPhaseofGlycolysisWritebalancedbiochemicalequationsforallthereactionsinthecatabolismofglucosetotw

2、omoleculesofglyceraldehyde3-phosphate(theprepara-toryphaseofglycolysis),includingthestandardfree-energychangeforeachreaction.Thenwritetheoverallornetequationforthepreparatoryphaseofglycolysis,withthenetstandardfree-energychange.AnswerTheinitialphaseofglycolysisrequiresAT

3、P;itisendergonic.Therearefivereactionsinthisphase:1.GlucoseATP88nglucose6-phosphateADPG16.7kJ/mol2.Glucose6-phosphate88nfructose6-phosphateG1.7kJ/mol3.Fructose6-phosphateATP88nfructose1,6-bisphosphateG14.2kJ/mol4.Fructose1,6-bisphosphate88ndihydroxyaceton

4、ephosphateglyceraldehyde3-phosphateG23.8kJ/mol5.Dihydroxyacetonephosphate88nglyceraldehyde3-phosphateG7.5kJ/molThenetequationforthisphaseisGlucose2ATP88n2glyceraldehyde3-phosphate2ADP2HTheoverallstandardfree-energychangecanbecalculatedbysummingtheindividualr

5、eac-tions:G2.1kJ/mol(endergonic).2.ThePayoffPhaseofGlycolysisinSkeletalMuscleInworkingskeletalmuscleunderanaerobicconditions,glyceraldehyde3-phosphateisconvertedtopyruvate(thepayoffphaseofglycolysis),andthepyruvateisreducedtolactate.Writebalancedbiochemicalequationsf

6、orallthereactionsinthisprocess,withthestandardfree-energychangeforeachreaction.Thenwritetheoverallornetequa-tionforthepayoffphaseofglycolysis(withlactateastheendproduct),includingthenetstandardfree-energychange.AnswerThepayoffphaseofglycolysisproducesATP,andthusisexergon

7、ic.Thisphasecon-sistsoffivereactions,designated6to10inthetext:6.Glyceraldehyde3-phosphatePNAD88n1,3-bisphosphoglycerateNADHHiG6.3kJ/mol7.1,3-BisphosphoglycerateADP88n3-phosphoglycerateATPG185kJ/mol8.3-Phosphoglycerate88n2-phosphoglycerateG4.4kJ/mol9.

8、2-Phosphoglycerate88nphosphoenolpyruvateG7.5kJ/mol10.PhosphoenolpyruvateADP88npyruvateATPG31