Microbiology Microbial Metabolism I -...

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MicrobiologyMicrobial Metabolism IIntroduction to MetabolismChing-Tsan Huang (黃慶璨)Office: Room 111, Agronomy HallTel: (02) 33664454E-mail: cthuang@ntu.edu.tw

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IntroductionWhy study microbiology?To control and utilization of MICR RGANI$M$

Physiology: The study of life processes in living cellsMetabolism: The total of all chemical reactions in cells

Why microbial metabolism?

TransportChemical Work

Mechanical

Heat

CatabolismAnabolism

PhotosynthesisMaintenance

GrowthRespiration

ReproductionFermentation

MetabolismPhysiologyLight Energy

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Substrates Products

EnergyCatabolismAnabolism

Light Energy

Photosynthesis

Enzymes

Overview of metabolism

Purpose: Trapping, generation and use of energyWhere: within cells (under controlled temperature and pH) How: catalyzed by enzymes

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Metabolism of microorganismsInterchangeable

Macro- to micro-molecules or vice versa

PolysaccharidesLipidsProteinsNucleic acids

MonosaccharidesFatty acids, glycerolAmino acidsNucleotides

CO2H2O, O2NH4

+, NO3-

PO4-, SO4

=

CatabolismAnabolism

Polymers Monomers Molecules

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Oxidation-Reduction ReactionElectron CarriersATP (adenosine triphosphate)

Reaction and Energy

Without enzyme

With enzyme

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Oxidation-Reduction Reaction

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Electron Transport Systems

NADH

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Electron CarriersTransfer electrons between different locationsEnergy flow in metabolism

NAD+ nicotinamide adenine dinucleotideNADP+ nicotinamide adenine dinucleotide phosphate

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ATP: Adenosine TriPhosphateA high-energy moleculeATP + H2O ADP + Pi ΔGo’ = -7.3 kcal/mol

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Apoenzymeprotein component of an enzyme

Cofactornonprotein component of an enzyme

prosthetic group – firmly attachedcoenzyme – loosely attached

Holoenzyme = apoenzyme + cofactorCoenzyme

often act as carriers, transporting substances around the cell

Enzyme Structure

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Enzymes: Classification

OxidoreductaseTransferase

HydrolaseLyase

IsomeraseLigase

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EnvironmentalEffects

pHTemperatureDenature

EnzymesCharacteristics

Lower activation energyKey-Lock relation: active or catalytic site Catalyze reactions by concentrating substrate and binding correctly

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Metabolic RegulationNature

Exceptionally complex and difficultAble to respond to environmental changes

SignificanceEssential for the cell to conserve energy and materialEssential for the cell to maintain metabolic balance

HowAmount of metabolites and enzymesActivity of enzymesFeedback inhibition

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Metabolic ChannelingCompartmentationthe differential distribution of enzymes and cofactors among separate cell structures

Enzyme activityis coordinated through regulation of the transport of metabolites and coenzymes between cell compartments

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Regulation Mechanisms

Central Dogma

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Allosteric Regulation

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Example

E. coli ACTase

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Covalent Modification

Reversible addition or removal of a chemical group alters enzyme activity

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Feedback (End Product) InhibitionMaintain appropriate concentration for each metabolitePacemaker enzyme or rate-determining reaction