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  • Chapter 5 Bacterial MetabolismMetabolism is sum total of all biochemical processes taking place in an organism.Two categoriesAnabolism synthesis of chemical compoundsForm bondsRequire energyEndergonicCatobolism hydrolysis of chemical compoundsBreak bondsRelease energyExergonic

  • Enzymes and Energy in Metabolism Pg 163 - 170Enzymes are a group of organic compounds made of proteins that increase the rate of a chemical reaction.

    Enzymes are reusable.

    One enzyme is used for one reaction.

    The substance acted on by an enzymes is called the substrate.

    Product formed is called the product.

  • EnzymeThe same enzyme can sometimes act to build up a product or break it down dependent on the circumstance.

    Enzymes are usually named for the reaction they perform and end in aseLike lactase which breaks down lactose or sucrase that break downs sucrose.There are exceptions lysozyme which lysis bacterial cell walls.

  • Enzymes Act Through Enzyme-Substrate ComplexHow an enzyme works is by aligning the substrate(s) in a specific way to make the reaction more likely to occur.

    In a hydrolysis reaction, the enzyme forces the substrate to stretch or weaken causing the bond to break.

    In a synthesis reaction, the enzyme brings the substrates together were the chemical bond will form.

    The area on the enzyme where the substrates reactions are brought together is called the active site

  • EnzymesSome enzymes are made up of only proteins like lysozyme.Other enzymes need small non-protein substances that help carry out the reaction.Some of these are metal ions, Mg2+, Fe2+ or ZN2+ and are called cofactors.If the non-protein is a small organic molecule it is called a coenzyme.Two important coenzymes are nicotinamide adenine dinucleotide (NAD+) and flavin adenine dinucleotide (FAD). NAD+ and FAD help carry electrons in metabolism.

  • Enzymes Often Act In Metabolic PathwaysA metabolic pathway is a sequence of chemical reactions, each reaction is carried out by a different enzyme, and the product of one reaction serves as a substrate for the next reaction

    The pathway starts with a specific substrate and ends with a final end product.

  • Adenosine Triphosphate Pg 168 169In many enzyme reactions energy is required to drive the reactionThis energy comes from adenosine triphosphateAdenosine triphosphate (ATP) is a high energy molecule and serves as an energy source for cellsThe energy is supplied when the covalent bond between the third and second phosphates of the ATP molecule is brokenThe breaking of this chemical bond releases 12,000 calories of usable energyIn a bacteria cell ATP is formed on the cell membraneIn a eukaryotic cell it is produced in the mitochondria

  • ATP

  • Catabolism of Glucose p. 170 to 179The best studied metabolic activity in a cell is the breakdown of glucoseGlucose is the key source of energy for production of ATPA mole of glucose (180 g) contains 686,000 calories of energyBreakdown of glucose is a controlled process that takes all the energy available in the molecule and converts it to ATPThe extraction of the energy of glucose happens down a metabolic pathway

  • GlycolysisGlycolysis is the first process of energy extraction from glucose.

    Glycolysis is the chemical breakdown of glucose.

    Glycolysis occurs in the cytosol of bacteria.

    In this process glucose is converted from a 6 carbon molecule into two 3 carbon molecules called pyruvate

  • Cellular RespirationThe production of ATP through the harvesting of energy down a metabolic pathway is called Cellular Respiration

    If a cell uses oxygen in making ATP it is called Aerobic Respiration

    C6H12O6 + 6O2 + 38 ADP + 38P 6CO2 + 6H2O + 38ATP

    If no oxygen is used it is called Anaerobic Respiration

  • The Steps of Glycolysis

  • GlycolysisEnergy Requiring Steps Each step in the breakdown uses a specific enzymeThe first three steps of gylcolysis requires 2 ATP moleculesGlucose is broken down into two 3 carbon molecules dihydroxyacetone phosphate (DHAP)Energy Producing StepsThe removal of the phosphate groups from these molecules helps to produce 2 ATP from each of the 3 carbon moleculesThe end product of glycolysis is 2 ATP, 2 Nicotinamide adenine dinucleotide (NADH) and 2 pyruvate moleculesNote: The 2 NADH molecules will be used in the production of energy in the electron transport chain

  • Krebs Cycle (Citric Acid Cycle)This metabolic pathway is called a cycle pathway because the starting product is identical to the finishing productAll steps are carried out by enzymesAll reactions take place along the bacterial cell membraneEukaryotic cells it occurs in the mitochondriaThe initial product added to the Krebs cycle is not pyruvatePyruvate first has to loss a carbon in the form of CO2 The remaining two carbons are attached to a molecule called coenzyme A

  • Krebs Cycle (Citric Acid Cycle)The new molecule is called acetyl coenzyme A (Acetyl CoA)

    The removal of the CO2 also produces another NADH molecule for the electron transport chain

    The remaining 2 carbons from the 3 carbon pyruvate are now able to enter the Krebs cycle

    This happens when a four carbon oxaloacetate molecule reacts with the acetyl CoA molecule and forms citrate (citric acid cycle)

  • Krebs Cycle (Citric Acid Cycle)From each removal of carbon along the cycle an NADH molecule is produced

    With pyruvate the end product of Krebs Cycle is 3 NADH molecules and 1 flavin adenine dinucleotide (FADH2)

    So all totaled from the breakdown of glucose through glycolysis and the Krebs cycle 10 NADH and 2 FADH2 are produced

  • Electron Transport Chain (Pg 175 179)Oxidative Phosphorylation is a sequence of reactions were electrons are moved from one molecule to another (electron transport) and the energy released is captured in ATP moleculesOxidative means the loss of electron pairs from a moleculeReduction means to the gain of a pair of electron Oxidative phosphorylation produces 34 molecules of ATP for each glucose molecule broken down

  • Oxidative Phosphorylation in Bacteria

  • Oxidative PhosphorylationOxidative phosphorylation, like the Krebs cycle, occurs in the cytoplasmic membrane in bacteria and mitochondria in eukaryotes

    The NADH and FADH2 molecules produced in glycolysis and the Krebs cycle are used to shunt electrons to the electron transport chain

    Once at the electron transport chain the electrons from either NADH and FADH2 are transferred to the first cytochrome in the cell membrane

    The oxidized NAD+ and FAD are returned to the cytosol to be reused in glycolysis and the Krebs cycle

  • Electron TransportThe electrons from the first cytochrome are transported to another cytochrome and then to the next down the chain This is why the process is referred to as the electron transport chain because it helps transfer electrons down a chain of cytochromes to be finally transferred to an oxygen moleculeThe final stage of the electron transport is were the electron pair is accepted by oxygenThe oxygen then requires two protons (H+) to stabilize itself and water is formed waterO2 is essential in the electron transport chainIf oxygen is not present the flow of electrons stops and the whole process stops

  • ATP SynthesisWhat makes the electron transport chain so important is that as electrons move down the cytochromes the energy released is used at three pumpsThese pumps move protons (H+) out of the cytosol to the outside of the membraneThis movement results in build up of protons (H+) outside the membrane and creates an electrical potentialThe protons are then moved back into the cell through a protein channel which has an enzyme called ATP synthase attached

  • ATP SynthesisAs the protons (H+) move back into the cell the free energy potential is used to synthesize ADP into ATP

    For each pair of electrons released by a NADH molecule 3 ATP molecules can be produced

    2 ATP for each FADH2

    Electron transport chain coupled to ATP synthesis

  • ATP Produced By Glycolysis

  • Anaerobic Respiration and Fermentation (Pg 183)Anaerobic respiration oxygen is not used as the final electron acceptor in electron transportNO3- ,SO2= , CO2

    When sulfate is used the final product is H2S the gas that gives the rotten egg smell

    Fermentation can make ATP in the absence of cellular respiration

    Krebs and oxidative respiration is shut down

  • Chapter 5 Summary of Key ConceptsEnzymes and Energy in MetabolismEnzymes Catalyze Chemical Reaction

    Enzymes Act Through Enzyme-Substrate Complex

    Enzymes Often Act in Metabolic Pathways

    Energy in The Form of ATP Is Required for Metabolism

  • The Catabolism of GlucoseGlucose Contains Stored Energy that Can Be ExtractedCellular Respiration Is a Series of Catabolic Pathway for the Production of ATPGlycolysis Is the First Stage of Energy ExtractionThe Krebs Cycle Extracts More Energy from PyruvateOxidative Phosphorylation Is the Process by which Most ATP Molecules Form

  • Other Aspects of CatabolismOther Carbohydrates, Proteins and Fats Can be used to Extract Energy From

    Anaerobic Respiration Produces Using Other Electron Acceptors

    Fermentation Produces ATP Using an Organic Final Electron Acceptor


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