INTRODUCTION TO METABOLISMMetabolic Pathways:Slide 3Chapter 9 – Cellular respiration Key ConceptsSlide 5Slide 6Introducing ATPStructure and Function of ATPATP Hydrolysis and Protein PhosphorylationGibbs Free-Energy Change – from chapter 2How Does ATP Drive Endergonic Reactions?Role of ATP as Energy CurrencySlide 13Slide 14Slide 15The Nature of Chemical Energy and Redox ReactionsWhat Is Energy? From chapter 2How Do Carbohydrates Store Energy? Chapter 5What Is a Redox Reaction?The Gain or Loss of an Electron Can Be RelativeElectrons Are Usually Accompanied by ProtonsSlide 22Slide 23Do Enzymes Act Alone? - from chapter 3What Happens When Glucose Is Oxidized?Slide 26An Overview of Cellular RespirationThe Steps of Cellular RespirationSlide 29Glycolysis: Processing Glucose to PyruvateThe Glycolysis ReactionsSlide 32Slide 33Methods of Producing ATPSlide 35Feedback InhibitionFeedback Inhibition Regulates GlycolysisSlide 38Slide 39The Remaining Reactions Occur in the MitochondriaSlide 41Pyruvate ProcessingSlide 43Pyruvate Processing Regulation© 2011 Pearson Education, Inc.INTRODUCTION TO METABOLISM •Living organisms use energy-extracting reactions to provide energy requirements for the process of life. 2 major questions:(1) How do cells extract energy and reducing power from their environment?(2) How do cells synthesize building blocks of their macromolecules?•The energy extraction process takes place in a series of small steps, in which en donors transfer energy to en acceptors. The oxidation-reduction reactions are essential to the extraction of energy from molecules such as glucose. Cofactors: NAD+ and FAD  Principle electron carriers•These processes are carried out by a highly integrated network of chemical reactions collectively known as "metabolism."© 2011 Pearson Education, Inc.Metabolic Pathways:•More than 1000 chemical reactions take place in even as simple organism like bacteria  E. Coli•Number of reactions in metabolism is large but number of kinds of reactions  small.•Metabolic pathways regulated in common ways.•Metabolism can be, Catabolism ( degradative pathway, increase in entropy, oxidative, extracts energy in the form of ATP) orAnabolism ( biosynthesis, decrease in entropy, reductive, needs energy, ATP provides E. and gets converted to ADP)© 2011 Pearson Education, Inc.MetabolismATP is not stored. A cell contains only enough ATP to last from 30 seconds to few minutes!Most cells are making ATP all the time!!!!More C-H bonds  more energy can be extracted.Why?© 2011 Pearson Education, Inc.Chapter 9 – Cellular respiration Key Concepts In cells, the endergonic reactions needed for life are paired with exergonic reactions (ATP).Cellular respiration produces ATP from molecules with high potential energy – often glucose.Cellular respiration has four components: 1. Glycolysis 2. Pyruvate processing3. The citric acid cycle4. Electron transport and chemiosmosisRespiration and fermentation are carefully regulated.Fermentation pathways allow glycolysis to continue when the lack of an electron acceptor shuts down electron transport chains.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Introducing ATP•ATP (adenosine triphosphate) is the cellular currency for energy – it provides the fuel for most cellular activities.•ATP has high potential energy and allows cells to do work.•ATP works by phosphorylating (transferring a phosphate group) target molecules.© 2011 Pearson Education, Inc.Structure and Function of ATP•The electrons in ATP have high potential energy because the four negative charges in its three phosphate groups repel each other.•Hydrolysis of the bond between the two outermost phosphate groups results in formation of ADP and Pi (inorganic phosphate, H2PO4−) in a highly exergonic reaction.–The released phosphate group is transferred to a protein.© 2011 Pearson Education, Inc.ATP Hydrolysis and Protein Phosphorylation •Hydrolysis of ATP is exergonic because the entropy of the product molecules is much higher than that of the reactants.•Energy released during ATP hydrolysis is transferred to a protein during phosphorylation.–This phosphorylation usually causes a change in the protein’s shape.© 2011 Pearson Education, Inc.Gibbs Free-Energy Change – from chapter 2•The Gibbs free-energy change (ΔG) determines whether a reaction is spontaneous or requires energy.ΔG < 0 is an exergonic spontaneous reaction.ΔG > 0 is an endergonic reaction that requires energy input.ΔG = 0 is a reaction that is at equilibrium.•Difference in Potential energy between reactants and product = ΔH•When the products are less ordered than the reactants, ΔS is positiveΔG = ΔH - T ΔS© 2011 Pearson Education, Inc.How Does ATP Drive Endergonic Reactions? When a protein is phosphorylated, the exergonic phosphorylation reaction is paired with an endergonic reaction in a process called energetic coupling. •In cells, endergonic reactions become exergonic when the substrates or enzymes involved are phosphorylated.© 2011 Pearson Education, Inc.Role of ATP as Energy CurrencyCoupling of extraction and Coupling of extraction and use of energy use of energy is the central feature is the central feature in the metabolism of all in the metabolism of all organisms.organisms.Oxidative processes take Oxidative processes take place when the organism place when the organism needs the energy that needs the energy that can be provided by the can be provided by the hydrolysis of ATP.hydrolysis of ATP. Exergonic reaction:(releases energy) Cell respiration CatabolismEndergonic reaction:(requires energy) Active transport Cell movements AnabolismATP (Adenosine triphosphate) is ATP (Adenosine triphosphate) is the predominant supplier of the predominant supplier of metabolic energymetabolic energyused in• Raises potential energyPhosphorylation of enzymesand substrates9.1drives9.1• Reactions that were endergonic with unphosphorylated enzymes/substrates become exergonic with phosphorylated enzymes/subtratesEnergetic couplingenablesCells use energy to do work• pump ions• synthesize molecules• move cargo• send and receive signalsATP9.1ATP  ADP +Pi large amount of E. released  cellular work© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.The energy extraction process takes place in a series of small steps, in which en donors transfer energy to en acceptors.