Metabolism : The sum of the chemical reactions in an organism

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Metabolism: The sum of the chemical reactions in an organism A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell Metabolic pathways are determined by enzymes

Catabolic and Anabolic ReactionsCatabolism: Provides energy and building blocks for anabolism. (Break down)Anabolism: Uses energy and building blocks to build large molecules. (Synthesis)

Metabolism: the sum of Catabolism and AnabolismOxidation: the loss or removal of electronsReduction: the gain of electrons

Figure 5.1Role of ATP in Coupling ReactionsOxidation-Reduction ReactionsOxidation: Removal of electronsReduction: Gain of electronsRedox reaction: An oxidation reaction paired with a reduction reaction

Oxidation-Reduction ReactionsIn biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations

The Generation of ATPATP is generated by the phosphorylation of ADP

Substrate-Level PhosphorylationEnergy from the transfer of a high-energy PO4 to ADP generates ATPOxidative PhosphorylationEnergy released from transfer of electrons (oxidation) of one compound to another (reduction) is used to generate ATP in the electron transport chainCarbohydrate CatabolismThe breakdown of carbohydrates to release energyGlycolysisKrebs cycleElectron transport chainFigure 5.11GlycolysisThe oxidation of glucose to pyruvic acid produces ATP and NADH

Figure 5.12, steps 15Preparatory Stage of Glycolysis2 ATP are usedGlucose is split to form 2 glyceraldehyde-3-phosphate

Figure 5.12, steps 610Energy-Conserving Stage of Glycolysis2 glucose-3-phosphate oxidized to 2 pyruvic acid4 ATP produced2 NADH produced

The Reactions of Glycolysis

The Krebs CycleOxidation of acetyl CoA produces NADH and FADH2Figure 5.13

The Krebs Cycle

The Reactions of the Krebs CycleThe Electron Transport ChainA series of carrier molecules that are, in turn, oxidized and reduced as electrons are passed down the chainEnergy released can be used to produce ATP by chemiosmosis

Figure 5.11Overview of Respiration and Fermentation

Figure 5.16Chemiosmotic Generation of ATP

Figure 5.15An Overview of ChemiosmosisA Summary of RespirationAerobic respiration: The final electron acceptor in the electron transport chain is molecular oxygen (O2).Anaerobic respiration: The final electron acceptor in the electron transport chain is not O2. Yields less energy than aerobic respiration because only part of the Krebs cycles operates under anaerobic conditions.Figure 5.16

RespirationPathwayATP ProducedNADH ProducedFADH2 ProducedGlycolysis220Intermediate step020Krebs cycle262Total4102Carbohydrate CatabolismEnergy produced from complete oxidation of one glucose using aerobic respirationPathwayBy Substrate-Level PhosphorylationBy Oxidative PhosphorylationFrom NADHFrom FADHGlycolysis260Intermediate step060Krebs cycle2184Total4304Carbohydrate CatabolismATP produced from complete oxidation of one glucose using aerobic respirationPathwayBy Substrate-Level PhosphorylationBy Oxidative PhosphorylationFrom NADHFrom FADHGlycolysis260Intermediate step06Krebs cycle2184Total4304Carbohydrate Catabolism36 ATPs are produced in eukaryotesFermentationOne process by which pyruvate is subsequently metabolized in the absence of oxygen

The result of the need to recycle the limited amount of NAD by passing the electrons of reduced NAD to other molecules

Homolactic acid fermentation: pyruvate is converted directly to lactic acid, using electrons from reduced NAD

Alcoholic fermentation: carbon dioxide is released from pyruvate to form acetaldehyde, which is reduced to ethanol

FermentationAny spoilage of food by microorganisms (general use)Any process that produces alcoholic beverages or acidic dairy products (general use)Any large-scale microbial process occurring with or without air (common definition used in industry)FermentationScientific definition:Releases energy from oxidation of organic moleculesDoes not require oxygenDoes not use the Krebs cycle or ETCUses an organic molecule as the final electron acceptor

Figure 5.18aAn Overview of FermentationFigure 5.19Types of Fermentation

Figure 5.27

Requirements of ATP ProductionFigure 5.28

A Nutritional Classification of Organisms

Figure 5.28A Nutritional Classification of OrganismsFigure 5.28

A Nutritional Classification of OrganismsNutritional TypeEnergy SourceCarbon SourceExamplePhotoautotrophLightCO2Oxygenic: Cyanobacteria plantsAnoxygenic: Green, purple bacteriaPhotoheterotrophLightOrganic compoundsGreen, purple nonsulfur bacteriaChemoautotrophChemicalCO2Iron-oxidizing bacteriaChemoheterotrophChemicalOrganic compoundsFermentative bacteriaAnimals, protozoa, fungi, bacteria.Metabolic Diversity among Organisms