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Mizzou MPP 3202 - Chapter 4

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Chapter 4: Energy and Cellular MetabolismProperties of Living OrganismsEnergy: Capacity to Do WorkEnergy Comes in Two FormsChemical ReactionsActivation energyExergonic ReactionsEndergonic ReactionsCoupled ReactionsActivation EnergiesEnzymesMetabolismATPATP ProductionPyruvateAnaerobic vs. AerobicProtein SynthesisCodonTranscriptionmRNA processingTranslationPost-Translational ModificationChapter 4: Energy and Cellular Metabolism•Energy in biological systems•Chemical reactions•Enzymes•MetabolismProperties of Living OrganismsEnergy is required for many, if not all (indirectly) processes important for life.Energy: Capacity to Do Work•Chemical work–Making and breaking of chemical bonds•Transport work–Moving ions, molecules, and larger particles–Useful for creating concentration gradients•Mechanical work–Moving organelles, changing cell shape, beating flagella and cilia–Contracting musclesEnergy Comes in Two Forms•Kinetic energy–Energy of motion–Work involves movement, i.e. molecules moving across membranes.•Potential energy–Stored energy –In concentration gradients and chemical bonds–Must be converted to kinetic energy to perform work–Transformation efficiencyWork is used to push a ballup a ramp. Kinetic energy ofmovement up the ramp isbeing stored in the potentialenergy of the ball’s position.The ball sitting at the top of theramp has potential energy, thepotential to do work.The ball rolling down the rampis converting the potentialenergy to kinetic energy.However, the conversion is nottotally efficient, and someenergy is lost as heat due tofriction between the ball, ramp,and air.Chemical Reactions•Bioenergetics is the study of energy flow through biological systems•Chemical reactions–Reactants become products–Reaction rate•Activation energy•Net free energy change of the reaction–Exergonic versus endergonic reactions–Coupled reactions–Reversible versus irreversible reactionsActivation energyActivation energy is the “push” needed to start a reaction.ReactantsStarting freeenergy levelFinal free energy levelProductsActivationenergyExergonic ReactionsExergonic reactions release energy because theproducts have less energy than the reactants.ActivationenergyTimeABCDNet freeenergychangeFree energy of moleculeKEYReactantsActivationof reactionReaction processProductsATP + H20  ADP + Pi + H+ + EnergyEndergonic ReactionsKEYReactantsActivationof reactionReaction processProductsEndergonic reactions trap some activationenergy in the products, which then have morefree energy than the reactants.Free energy of moleculeEFActivation energyGHNet freeenergy changeTimeSynthesis Reactions: Glucose  GlycogenCoupled Reactions•Acquire activation energy•Direct coupling: simultaneous/colocalized, ATPExergonic reactions releaseenergy.Endergonic reactions will notoccur without input of energy.Nucleotides captureand transfer energyand electronsENERGYreleasedENERGYutilizedAB CDEF GHHeat energyHigh-energyelectronsATPNADPHNADHFADH2•Indirect coupling: Stored energy in nucleotides (NADH, FADH2, NADPH; the first two transfer energy to ATP). E + F G + HATP ADP + PiActivation Energies•Reversible–Most biological reactions–Enzymes•Irreversible (large activation energy)CDABKEYReactantsActivationof reactionReaction processProductsActivation energyTimeNet freeenergychangeFree energy of moleculeEnzymes•Enzymes speed up the rate of chemical reactions–Catalysts –Reactants are called substrates•Isozymes •Catalyze same reaction, but under different conditions•May be activated, inactivated, or modulated–Coenzymes  (e.g., vitamins)–Chemical modulators  temperature and pHKEYReactantsActivationof reactionReaction processProductsCDA BTimeFree energy of moleculeActivation energywithout enzymeLower activationenergy in presenceof enzymeMetabolism•All chemical reactions that take place in an organism•Catabolism: release energy through breakdown of biomolecules. Energy can be “trapped” in ATP, NADH, NADPH•Anabolism: require energy, synthesis of biomolecules.•Kilocalories are measures of energy released from or stored in chemical bonds•Molecules in pathways are intermediatesATP•Nucleotide with three phosphate groups•Carrier of energy, not storage•High-energy phosphate bond•ADP + Pi + energy ADP~P (or ATP)•Aerobic metabolism (+ Oxygen)–Glycolysis–Citric acid cycle–Electron transport chain•Anaerobic metabolism (- Oxygen)–GlycolysisATP Production Carbon Oxygen Coenzyme AH and –OH not shownPyruvateLactatePyruvateNADHNAD+AnaerobicAerobicCytosolMitochondrialmatrixCoAAcetyl CoACoAAcyl unitCITRIC ACIDCYCLEPyruvateAnaerobic vs. Aerobic1 Glucose2 Pyruvate2 LactateNADHFADH2CO2ATP24222ATP0NADHTOTALSAnaerobicMetabolismAerobicMetabolism2 Pyruvate1 GlucoseGLYCOLYSISGLYCOLYSISNADHFADH2CO2ATP242*2 22264Citric acidcycleHigh-energy electronsand H+6 O2ELECTRONTRANSPORTSYSTEM26-2830-32ATP6H2O6CO22 Acetyl CoA* Cytoplasmic NADH sometimes yields only 1.5 ATP/NADH instead of 2.5 ATP/NADH.TOTALSGENE ACTIVATIONTRANSCRIPTION(See Fig. 4.19)mRNA PROCESSING(See Fig. 4.20)TRANSLATION(See Fig. 4.21)POST-TRANSLATIONALMODIFICATIONFolding andcross-linksCleavage intosmaller peptidesAssembly intopolymeric proteinsAddition of groups: • sugars • lipids • -CH3 • phosphateCytosolNucleus• rRNA in ribosomes• tRNA• Amino acidsProcessedmRNAAlternativesplicingInterferencemRNA “silenced”si RNAmRNAInduction RepressionRegulatedactivityConstitutivelyactiveGene Regulatory proteinsProtein chainProtein SynthesisCodonSecond base of codonFirst base of codonThird base of codonPheLeuLeuIleMetValSerProThrAlaTyrHisGlnAsnLysAspGluCysTrpArgSerArgGlyStartStopStopDNA: T, A, C, GRNA: U, A, C, GRNA polymerase binds toDNA.The section of DNA thatcontains the gene unwinds.RNA bases bind to DNA,creating a single strand ofmRNA.DNATemplatestrandSite ofnucleotide assemblymRNAtranscriptRNApolymeraseRNApolymeraseRNA basesLengtheningmRNA strandRNApolymerasemRNA strandreleasedLeaves nucleusafter processingmRNA and the RNA polymerasedetach from DNA, and themRNA goes to the cytosol afterprocessing.TranscriptionRNA polymerase (Mg2+ or Mn2+)PromoterTranscription factorsGeneTemplatestrandDNAPromoterTranscribed sectionTRANSCRIPTIONUnprocessedmRNAmRNA Processingmay produce twoproteins from onegene byalternative splicing.Introns removedIntrons removedExons for protein #1Exons for protein #2a


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Mizzou MPP 3202 - Chapter 4

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