Bacterial Bacterial Metabolism and Metabolism and

Energy Energy GenerationGeneration

  

An Overview of An Overview of MetabolismMetabolism

Metabolism – Metabolism – the sum of all chemical the sum of all chemical reactions occurring within a cell reactions occurring within a cell simultaneously. Involves degradation simultaneously. Involves degradation and biosynthesis of complex molecules.and biosynthesis of complex molecules.

CatabolismCatabolism-the breakdown of larger, -the breakdown of larger, more complex molecules into smaller, more complex molecules into smaller, simpler ones, during which energy is simpler ones, during which energy is released, trapped, and made available released, trapped, and made available for workfor work

AnabolismAnabolism-the synthesis of complex -the synthesis of complex molecules from simpler ones during molecules from simpler ones during which energy is added as inputwhich energy is added as input

Multi-stage process of Multi-stage process of catabolismcatabolism

Stage 1Stage 1-breakdown of large -breakdown of large molecules (polysaccharides, molecules (polysaccharides, lipids, proteins) into their lipids, proteins) into their component constituents with the component constituents with the release of little (if any) energyrelease of little (if any) energy

Stage 2Stage 2-degradation of the -degradation of the products of stage 1 products of stage 1 aerobically or anaerobically aerobically or anaerobically to even simpler molecules to even simpler molecules with the production of some with the production of some ATP, NADH, and/or FADHATP, NADH, and/or FADH22

Stage 3Stage 3-complete aerobic -complete aerobic oxidation of stage 2 products oxidation of stage 2 products with the production of ATP, with the production of ATP, NADH, and FADHNADH, and FADH22; the latter ; the latter two molecules are processed two molecules are processed by electron transport to yield by electron transport to yield much of the ATP producedmuch of the ATP produced

Metabolic efficiencyMetabolic efficiency is maintained by the is maintained by the use of a few common catabolic pathways, use of a few common catabolic pathways, each degrading many nutrientseach degrading many nutrients

Microorganisms are catabolically diverse, Microorganisms are catabolically diverse, but are anabolically quite uniformbut are anabolically quite uniform

AmphibolicAmphibolic pathways function both pathways function both catabolically and anabolically, and catabolically and anabolically, and sometimes employ separate enzymes to sometimes employ separate enzymes to catalyze the forward and reverse catalyze the forward and reverse reactions; this separation enables reactions; this separation enables independent regulation of the forward independent regulation of the forward and reverse reactionsand reverse reactions

DefinitionsDefinitions OxidationOxidation ReductionReduction Redox reactionsRedox reactions Standard Reduction potentialStandard Reduction potential Oxidative phosphorylationOxidative phosphorylation ChemiosmosisChemiosmosis Electron transport chainElectron transport chain

OxidationOxidation The loss of electrons from an atom The loss of electrons from an atom

or chemical compound. or chemical compound. Results in the generation of energy.Results in the generation of energy.

ReductionReduction The gain of electronsThe gain of electrons Requires energyRequires energy

Redox reactionsRedox reactions Reactions involving the transfer of Reactions involving the transfer of

electrons from a donor to an acceptorelectrons from a donor to an acceptor = Redox couple= Redox couple

Reducing agent = reductant = donorReducing agent = reductant = donor Oxidizing agent = oxidant = acceptorOxidizing agent = oxidant = acceptor

Oxidant + neOxidant + ne-- (number of electrons (number of electrons transferred)transferred) Reductant Reductant

Standard Reduction Potential Standard Reduction Potential (Equilibrium Constant = E(Equilibrium Constant = Eoo’ at ’ at

pH 7.0)pH 7.0) Measures the tendency of the Measures the tendency of the

reductant to lose electrons.reductant to lose electrons. Redox couples with more negative Redox couples with more negative

EEoo’ values will donate elecrron to ’ values will donate elecrron to redox couples with more positive Eredox couples with more positive Eoo’ ’ values, releasing free enegy (G)values, releasing free enegy (G) Energy is required to reverse the Energy is required to reverse the

process (e.g. photosynthesis)process (e.g. photosynthesis)

The larger the difference in EThe larger the difference in Eoo’ ’ values between electron donors and values between electron donors and electron acceptors, the greater the electron acceptors, the greater the free energy that is generated.free energy that is generated.

Therefore, the more negative the Therefore, the more negative the reduction potential, the better reduction potential, the better electron donor it is, and the more electron donor it is, and the more numerous the potential acceptors.numerous the potential acceptors.

Oxidative Oxidative phosphorylationphosphorylation

A metabolic sequence of reactions occurring A metabolic sequence of reactions occurring within a membrane in which an electrons within a membrane in which an electrons transferred from a reduced coenzyme by a transferred from a reduced coenzyme by a series of electron carriers, establishing an series of electron carriers, establishing an electrochemical gradient across the membrane electrochemical gradient across the membrane that drives the formation of ATP from ADP and that drives the formation of ATP from ADP and inorganic phosphate by chemiosmosis.inorganic phosphate by chemiosmosis.

Powered by redox reactionsPowered by redox reactions Aerobic respiration uses OAerobic respiration uses O22 as TEA as TEA Anaerobic respiration uses SOAnaerobic respiration uses SO44

2-2-, NO, NO33--, CO, CO22 as as

TEA (not as efficient as using OTEA (not as efficient as using O22 as TEA) as TEA)

ChemiosmosisChemiosmosis The generation of ATP by the The generation of ATP by the

movement of hydrogen ions into movement of hydrogen ions into pores in the cytoplasmic membrane pores in the cytoplasmic membrane that are associated with the ATPase that are associated with the ATPase system.system.

Electron Transport ChainElectron Transport Chain A series of oxidation-reduction reactions in A series of oxidation-reduction reactions in

which electrons are transported from a which electrons are transported from a substrate through a series of intermediate substrate through a series of intermediate electron carriers to a final acceptor, establishing electron carriers to a final acceptor, establishing an electrochemical gradient across a membrane an electrochemical gradient across a membrane that results in the formation of ATP.that results in the formation of ATP.

Electrochemical gradient = proton motive forceElectrochemical gradient = proton motive force Examples of donors = coenzymes NADH, Examples of donors = coenzymes NADH,

NADPH, and FADHNADPH, and FADH22 --> often referred to as --> often referred to as “reducing power”“reducing power”

Electron Transport Electron Transport and Oxidative and Oxidative

PhosphorylationPhosphorylation

Mitochondrial Electron Transport Mitochondrial Electron Transport (Figure 9.13)(Figure 9.13)

#1: Prokaryotes use different #1: Prokaryotes use different electron carriers (cytochromes vary)electron carriers (cytochromes vary)

Three differences between Three differences between prokaryotes and eukaryotesprokaryotes and eukaryotes

#2: #2: The bacterial electron transport The bacterial electron transport chain may be extensively branched chain may be extensively branched with several terminal oxidaseswith several terminal oxidases Electrons may enter at several different Electrons may enter at several different

points and use different TEAspoints and use different TEAs Often dependent on growing conditions Often dependent on growing conditions

of bacteriaof bacteria Different cytochromes used depending Different cytochromes used depending

on Oon O2 2 status (log vs stationary)status (log vs stationary)

#3: #3: Electron transport in Electron transport in bacteria occurs in the cytoplasmic bacteria occurs in the cytoplasmic membranemembrane In eukaryotic cells this occurs on the In eukaryotic cells this occurs on the

inner membranes of mitochondriainner membranes of mitochondria But the mechanism of Ox-Phos is But the mechanism of Ox-Phos is

remarkably similarremarkably similar Did mitochondria arise from bacteria? Did mitochondria arise from bacteria?

Endosymbiont theoryEndosymbiont theory

Electrons from NADH and Electrons from NADH and FADHFADH22 are transported in a are transported in a series of redox reactions to a series of redox reactions to a terminal electron acceptorterminal electron acceptor Reduced coenzymes (NADH and Reduced coenzymes (NADH and

FADH2) generated in glycolysis FADH2) generated in glycolysis and TCA cycles must be and TCA cycles must be reoxidizedreoxidized

Oxidative PhosphorylationOxidative Phosphorylation Some of the energy liberated Some of the energy liberated

during electron transport is during electron transport is used to drive the synthesis of used to drive the synthesis of ATP in a process called ATP in a process called oxidative phosphorylationoxidative phosphorylation

The The chemiosmotic hypothesischemiosmotic hypothesis of of oxidative phosphorylation oxidative phosphorylation (Peter Mitchell)(Peter Mitchell)Membrane-bound carriers transfer Membrane-bound carriers transfer electrons to oxygen across a chainelectrons to oxygen across a chainCytochromes, flavoprotein, quinones, Cytochromes, flavoprotein, quinones, non-heme iron containing proteinsnon-heme iron containing proteins

Coupling of electron transport to Coupling of electron transport to oxidative phosphorylationoxidative phosphorylation

Postulates that the energy released Postulates that the energy released during electron transport is used to during electron transport is used to establish a proton gradient (proton establish a proton gradient (proton motive force due to different charge motive force due to different charge distributions)distributions) As electrochemical potential is formed As electrochemical potential is formed

(PMF) protons are attracted back into (PMF) protons are attracted back into the cell through a proton channel the cell through a proton channel

FF11FF00 adenosine triphosphatase (F adenosine triphosphatase (F11FF00 ATPase) in proton channel releases energy ATPase) in proton channel releases energy as protons enteras protons enter

BlockersBlockers inhibit the flow of electrons inhibit the flow of electrons

through the systemthrough the system Examples: Cyanide or Azide (block Examples: Cyanide or Azide (block

electron transport between cyt a and O2electron transport between cyt a and O2 Examples: Piericidin (competes with Examples: Piericidin (competes with

Coenzyme Q) and Antimycin A (blocks Coenzyme Q) and Antimycin A (blocks electron transport between cyt b and cyt electron transport between cyt b and cyt c)c)

This proton-motive force is then This proton-motive force is then used to used to drive ATP synthesisdrive ATP synthesis Energy is converted to chemical Energy is converted to chemical

energy by phosphorylation of ADP to energy by phosphorylation of ADP to ATPATP

High energy phosphate bonds used for High energy phosphate bonds used for biosynthetic pathwaysbiosynthetic pathways

Net result:Net result: 1 NADP or NADPH = 3 ATP1 NADP or NADPH = 3 ATP 1 FADH1 FADH22 = 2 ATP = 2 ATP

InhibitorsInhibitors of ATP synthesis fall into of ATP synthesis fall into two main categories:two main categories:

Inhibition of aerobic Inhibition of aerobic synthesis of ATPsynthesis of ATP

UncouplersUncouplers allow electron flow, but disconnect it from allow electron flow, but disconnect it from

oxidative phosphorylation (inhibit ATP oxidative phosphorylation (inhibit ATP synthesis, not electron transport)synthesis, not electron transport)

Uncouple electron transport from Ox-Phos Uncouple electron transport from Ox-Phos The energy from electron transport is The energy from electron transport is lost as heat, not ATPlost as heat, not ATP

Examples: Valinomycin, Dinitrophenol (DNP)Examples: Valinomycin, Dinitrophenol (DNP)

The The Yield of ATPYield of ATP in Glycolysis and in Glycolysis and Aerobic RespirationAerobic Respiration The yield of ATP in glycolysis and The yield of ATP in glycolysis and

aerobic respiration varies with each aerobic respiration varies with each organism, but has a theoretical organism, but has a theoretical maximum of 38 molecules of ATP per maximum of 38 molecules of ATP per molecule of glucose catabolizedmolecule of glucose catabolized

Anaerobic organisms using glycolysis Anaerobic organisms using glycolysis can only produce two molecules of can only produce two molecules of ATP per molecule of glucose ATP per molecule of glucose catabolizedcatabolized

Pasteur EffectPasteur Effect Switch from fermentation Switch from fermentation

(anaerobic) to aerobic respiration (anaerobic) to aerobic respiration when oxygen is availablewhen oxygen is available Much more efficientMuch more efficient More ATP using oxygen as TEAMore ATP using oxygen as TEA Sugar catabolism dramatically Sugar catabolism dramatically

decreasesdecreases

Distinction between Distinction between Respiration and Respiration and FermentationFermentation

Respiration:Respiration: Electrons from oxidative process enter Electrons from oxidative process enter

the electron transport system, protons the electron transport system, protons are generated and energy is generated are generated and energy is generated through OX-PHOSthrough OX-PHOS

Electrons are passed to an Electrons are passed to an inorganic inorganic acceptoracceptor

Electron transport is usedElectron transport is used OX-PHOS is usedOX-PHOS is used

FermentationFermentation Electrons and protons from oxidized Electrons and protons from oxidized

substrates are transferred directly to substrates are transferred directly to another another organic compoundorganic compound (organic (organic acceptor) in the pathwayacceptor) in the pathway

No electron transportNo electron transport No OX-PHOSNo OX-PHOS Substrate-level phosphorylation used insteadSubstrate-level phosphorylation used instead

The oxidation of a phosphorylated compound resuluting The oxidation of a phosphorylated compound resuluting in the direct formation of a high-energy phosphate bondin the direct formation of a high-energy phosphate bond

Transferred to ADP to form ATPTransferred to ADP to form ATP

Example of fermentation:Example of fermentation: Glycolysis:Glycolysis:

Glucose Glucose Pyruvate Pyruvate Lactic Acid or Ethanol Lactic Acid or Ethanol The final electron acceptor = pyruvate (or a The final electron acceptor = pyruvate (or a

product of pyruvate such as acetaldehyde product of pyruvate such as acetaldehyde intermediate)intermediate)

Summary: In fermentation, organic Summary: In fermentation, organic compounds are the electron donors compounds are the electron donors AND acceptors with some energy AND acceptors with some energy generatedgenerated

The Breakdown of The Breakdown of Glucose to PyruvateGlucose to Pyruvate

The The glycolyticglycolytic ( (Embden-Embden-MeyerhofMeyerhof) pathway is the most ) pathway is the most common pathway and is divided common pathway and is divided into two parts:into two parts:The The 6-carbon sugar stage6-carbon sugar stage involves involves the phosphorylation of glucose the phosphorylation of glucose twice to yield fructose 1,6-twice to yield fructose 1,6-bisphosphatebisphosphaterequires the expenditure of two requires the expenditure of two molecules of ATPmolecules of ATP

The The 3-carbon sugar stage3-carbon sugar stage cleaves cleaves fructose 1,6-bisphosphate into fructose 1,6-bisphosphate into two 3-carbon molecules, which two 3-carbon molecules, which are each processed to pyruvateare each processed to pyruvatetwo molecules of ATP are produced two molecules of ATP are produced by substrate-level phosphorylation by substrate-level phosphorylation from each of the 3-carbon molecules from each of the 3-carbon molecules for a net yield of two molecules of for a net yield of two molecules of ATPATP

2 molecules of NADH are also 2 molecules of NADH are also produced per glucose moleculeproduced per glucose molecule

1 Glucose 1 Glucose 2 Pyruvate 2 Pyruvate 2 ATP used2 ATP used 4 ATP generated4 ATP generated Net yield = 2 ATPNet yield = 2 ATP

2 NAD used2 NAD used 2 NADH generated2 NADH generated Net yield = 2 NADH (THIS MUST BE Net yield = 2 NADH (THIS MUST BE

OXIDIZED TO KEEP THIS PATHWAY OXIDIZED TO KEEP THIS PATHWAY RUNNING.)RUNNING.)

The The pentose phosphatepentose phosphate (hexose (hexose monophosphate) monophosphate) pathway pathway uses a uses a different set of reactions to produce different set of reactions to produce a variety of 3-, 4-, 5-, 6-, and 7-a variety of 3-, 4-, 5-, 6-, and 7-carbon sugar phosphatescarbon sugar phosphates

These phosphates can be used to These phosphates can be used to produce ATP and NADPH, as well as produce ATP and NADPH, as well as to provide the carbon skeletons for to provide the carbon skeletons for the synthesis of amino acids, nucleic the synthesis of amino acids, nucleic acids, and other macromoleculesacids, and other macromolecules

The NADPH can be used to The NADPH can be used to provide electrons for provide electrons for biosynthetic processes or can biosynthetic processes or can be converted to NADH to be converted to NADH to yield additional ATP through yield additional ATP through the electron transport chainthe electron transport chain

The The Entner-DoudoroffEntner-Doudoroff pathway can also be used to pathway can also be used to produce pyruvate with a produce pyruvate with a lower yield of ATP, but is lower yield of ATP, but is accompanied by the accompanied by the production of NADPH as well production of NADPH as well as NADH.as NADH.

FermentationFermentation

In the absence of oxygen, In the absence of oxygen, NADH is not usually oxidized NADH is not usually oxidized by the electron transport chain by the electron transport chain because no external electron because no external electron acceptor is availableacceptor is available

However, NADH must still be However, NADH must still be oxidized to replenish the supply oxidized to replenish the supply of NADof NAD++ for use in glycolysis for use in glycolysis

Fermentations are reactions that Fermentations are reactions that regenerate NADregenerate NAD++ from NADH in from NADH in the absence of oxygenthe absence of oxygen

Fermentations involve pyruvate Fermentations involve pyruvate or pyruvate derivatives as or pyruvate derivatives as electron acceptorselectron acceptors

Fermentations may or may not Fermentations may or may not produce additional ATP for the produce additional ATP for the cellcell

Six Common Pathways of Six Common Pathways of FermentationFermentation

Homoloactic acidHomoloactic acid AlcoholoicAlcoholoic Propionic acidPropionic acid Butylene glycol (Butanediol)Butylene glycol (Butanediol) Mixed acid fermentationMixed acid fermentation Butyric acid, butanol, acetoneButyric acid, butanol, acetone

#1: Homolactic acid #1: Homolactic acid fermentationfermentationPyruvate Pyruvate lactic acid lactic acid

#2: Alcoholic fermentation#2: Alcoholic fermentationPyruvate Pyruvate acetaldehyde acetaldehyde ethanolethanol

#3: Propionic acid fermentation#3: Propionic acid fermentation Pyruvate Pyruvate acetic acid, OAA, acetic acid, OAA,

malate, fumarate, succinate, malate, fumarate, succinate, propionatepropionate

#4: Butylene glycol #4: Butylene glycol fermentation (butanediol)fermentation (butanediol) Pyruvate Pyruvate acetolactic acid acetolactic acid

acetoin acetoin 2,3 butylene glycol (2,3 2,3 butylene glycol (2,3 butanediol)butanediol)

#5:#5: Mixed acid fermentationMixed acid fermentation Pyruvate Pyruvate Lactate, formate, acetate, Lactate, formate, acetate,

ethanol, succinateethanol, succinate #6: Butyric acid, butanol, acetone #6: Butyric acid, butanol, acetone

fermentationfermentation Pyruvate Pyruvate acetyl CoA, adetate, ethanol acetyl CoA, adetate, ethanol Pyruvate Pyruvate acetyl CoA, acetone, acetyl CoA, acetone,

isopropanolisopropanol Pyruvate Pyruvate acetyl CoA, butyryl CoA, acetyl CoA, butyryl CoA,

butanol, butyric acidbutanol, butyric acid

Mixed Acid versus Butanediol Mixed Acid versus Butanediol Fermenters: 3 Tests to Divide Fermenters: 3 Tests to Divide

GroupsGroups Voges-Proskauer TestVoges-Proskauer Test

Detection of acetoin (intermediary Detection of acetoin (intermediary metabolite)metabolite)

Methyl red testMethyl red test Mixed acid fermenter produces a lot of acidMixed acid fermenter produces a lot of acid pH is ~4.4pH is ~4.4 Red color produced for MAF onlyRed color produced for MAF only

COCO22/H/H22 ratios ratios Mixed acid ~1:1Mixed acid ~1:1 Butanediol ~5:1Butanediol ~5:1

RespirationRespiration Use of electron transport chain Use of electron transport chain

passing electrons to an inorganic passing electrons to an inorganic terminal electron acceptor (TEA)terminal electron acceptor (TEA)

Energy generated through OX-Energy generated through OX-PHOSPHOS

More energy efficient than More energy efficient than fermentationfermentation

Aerobic RespirationAerobic Respiration Oxygen = Terminal Electron Oxygen = Terminal Electron

AcceptorAcceptor Glucose Glucose CO CO22

38 ATP38 ATP

Anaerobic RespirationAnaerobic Respiration Uses inorganic molecules other than Uses inorganic molecules other than

oxygen as terminal electron oxygen as terminal electron acceptors; this produces additional acceptors; this produces additional ATP for the cell, but not usually as ATP for the cell, but not usually as much as is produced by aerobic much as is produced by aerobic respirationrespiration

Used mainly by anaerobes but many Used mainly by anaerobes but many facultative anaerobes may use facultative anaerobes may use anaerobic respiration (electron anaerobic respiration (electron transport and OX-PHOS still used)transport and OX-PHOS still used)

Non-oxygen Terminal Electron Non-oxygen Terminal Electron AcceptorAcceptor

Three major types:Three major types: NONO33

-- nitrate reducers nitrate reducers Facultative anaerobesFacultative anaerobes TEA = nitrateTEA = nitrate Results in denitrification (loss of nitrates froom Results in denitrification (loss of nitrates froom

the soil = agricultural dilamma)the soil = agricultural dilamma) Advantageous when removing nitrates from Advantageous when removing nitrates from

sewagesewage

2 NO2 NO33-- + 12e- + 12H + 12e- + 12H++ N N22 + 6H + 6H22OO

Examples:Examples: EscherichiaEscherichia EnterobacterEnterobacter BacillusBacillus PseudomonasPseudomonas MicrococcusMicrococcus RhizobiumRhizobium

SOSO442- 2- sulfate reducers sulfate reducers

TEA = sulfate TEA = sulfate which is reduced to sulfidewhich is reduced to sulfide

SOSO442-2- + 8e- + 8H+ + 8e- + 8H+ S S2-2- + 4H + 4H22OO

Examples:Examples: DesulfovibrioDesulfovibrio DesulfotomaculumDesulfotomaculum

COCO22 methane bacteria methane bacteria TEA = CO2 which is reduced to methaneTEA = CO2 which is reduced to methane Habitat = rumen of cud-chewing animals, Habitat = rumen of cud-chewing animals,

black mud of ponds and composts and black mud of ponds and composts and sewage tankssewage tanks

COCO22 + 8e- + 8H + 8e- + 8H++ CH CH44 + 2H + 2H22OO

MetalsMetals can also be reduced can also be reduced Elemental sulfur (SElemental sulfur (Soo)) Ferric iron (FeFerric iron (Fe3+3+))

The Tricarboxylic The Tricarboxylic Acid Cycle-a series of Acid Cycle-a series of

reactionsreactions

Acetyl-CoAAcetyl-CoA (produced by (produced by decarboxylation of pyruvate) decarboxylation of pyruvate) reacts with oxaloacetate to reacts with oxaloacetate to produce a 6-carbon moleculeproduce a 6-carbon molecule

Subsequently, two molecules of Subsequently, two molecules of carbon dioxide are released, carbon dioxide are released, regenerating the oxaloacetateregenerating the oxaloacetate

ATP is produced by substrate-ATP is produced by substrate-level phosphorylationlevel phosphorylation

Three molecules of NADH and one Three molecules of NADH and one molecule of FADHmolecule of FADH22 are produced are produced per acetyl-CoA, and can be further per acetyl-CoA, and can be further processed to produce more ATPprocessed to produce more ATP

Even those organisms that lack the Even those organisms that lack the complete TCA cycle usually have complete TCA cycle usually have most of the cycle enzymes because most of the cycle enzymes because one of the TCA cycle's major one of the TCA cycle's major functions is to provide carbon functions is to provide carbon skeletons for use in biosynthesisskeletons for use in biosynthesis

Catabolism of Catabolism of Carbohydrates and Carbohydrates and

Intracellular Reserve Intracellular Reserve PolymersPolymers

proceeds by either proceeds by either hydrolysishydrolysis oror

phosphorolysisphosphorolysis to produce to produce molecules that can enter the molecules that can enter the common catabolic pathways common catabolic pathways already discussedalready discussed

Lipid CatabolismLipid Catabolism

LipasesLipasesDegrade lipids to glycerol + Degrade lipids to glycerol + free fatty acidsfree fatty acids

Fatty acid degradation Fatty acid degradation proceeds by the proceeds by the beta -beta -oxidation pathwayoxidation pathway, which , which produces acetyl-CoA, which produces acetyl-CoA, which can enter the TCA cyclecan enter the TCA cycle

Glycerol degradation proceeds Glycerol degradation proceeds via the via the Embden-Meyerhof Embden-Meyerhof pathwaypathway (glycolysis) entering as (glycolysis) entering as glyceraldehyde 3-phosphateglyceraldehyde 3-phosphate

Protein and Amino Protein and Amino Acid CatabolismAcid Catabolism

Proteins are degraded by secreted Proteins are degraded by secreted proteasesproteases to their component to their component amino acids, which are transported amino acids, which are transported into the cell and catabolizedinto the cell and catabolized

The amino group is removed by The amino group is removed by deaminationdeamination or or transaminationtransamination

The resulting organic acids are The resulting organic acids are converted to pyruvate, acetyl-CoA, converted to pyruvate, acetyl-CoA, or a TCA-cycle intermediateor a TCA-cycle intermediate

AnabolismAnabolism Building up structural and Building up structural and

functional components of a cell functional components of a cell using energy and building blocks using energy and building blocks (small molecular intermediates)(small molecular intermediates)

Includes synthesis of nucleic acids Includes synthesis of nucleic acids (DNA + RNA), cell wall (lipid (DNA + RNA), cell wall (lipid bilayer + PTG) and proteins.bilayer + PTG) and proteins.

Two important features:Two important features: Biosynthetic pathways of most cellular Biosynthetic pathways of most cellular

components is different from components is different from degradative pathways at key regulatory degradative pathways at key regulatory steps (regulated by endproducts + steps (regulated by endproducts + [ATP] + [NAD+][ATP] + [NAD+]

Biosynthetic pathways are often Biosynthetic pathways are often induced by combining reactants to form induced by combining reactants to form activated intermediatesactivated intermediates

Polysaccharide biosynthesisPolysaccharide biosynthesis Some monosaccharides are derived from metabolic Some monosaccharides are derived from metabolic

pathway intermediatespathway intermediates React with nucleoside triphosphates to form activated React with nucleoside triphosphates to form activated

intermediates (or adenosine or uridine diphosphate)intermediates (or adenosine or uridine diphosphate) Examples in bacteriaExamples in bacteria

Capsular polysaccharidesCapsular polysaccharides Outer membrane LPSOuter membrane LPS GlycogenGlycogen PTG (NAG:UDP intermediate)PTG (NAG:UDP intermediate)

Gluconeogenesis also used Gluconeogenesis also used Synthesis of glucose from a non-carbohydrate precursorSynthesis of glucose from a non-carbohydrate precursor

Lipid biosynthesisLipid biosynthesis Two lipids predominate in bacteria in Two lipids predominate in bacteria in

the lipid bilayer:the lipid bilayer: Phosphatidyl glycerolPhosphatidyl glycerol PhosphatidylethanolaminePhosphatidylethanolamine

Glycerol phosphate backbone plus two Glycerol phosphate backbone plus two fatty acids (12-18 carbons in length)fatty acids (12-18 carbons in length)

Glycerol derived from dihydroxyacetone Glycerol derived from dihydroxyacetone phosphate (Embden-Meyerhoff)phosphate (Embden-Meyerhoff)

Fatty acids added from fatty acyl-CoA Fatty acids added from fatty acyl-CoA intermediates (FAs built up 2 carbons at a intermediates (FAs built up 2 carbons at a time using acetyl CoA)time using acetyl CoA)

Amino acid and protein biosynthesisAmino acid and protein biosynthesis AutotrophsAutotrophs

Capable of synthesizing all 20 amino acids Capable of synthesizing all 20 amino acids starting with COstarting with CO22 (can survive in completely (can survive in completely inorganic environment)inorganic environment)

Majority of prototrophsMajority of prototrophs Similarly do not require added amino acidsSimilarly do not require added amino acids Some bacteria (e.g. Neisseria and Streptococci) Some bacteria (e.g. Neisseria and Streptococci)

require preformed amino acidsrequire preformed amino acids AuxotrophsAuxotrophs

Mutant strains that DO require growth factors Mutant strains that DO require growth factors and sometimes amino acidsand sometimes amino acids

Amino acids are synthesized by Amino acids are synthesized by complex pathways often involving complex pathways often involving multiple unique enzymesmultiple unique enzymes Histidine synthesis requires 9 enzymesHistidine synthesis requires 9 enzymes

Synthesis begins with metabolic Synthesis begins with metabolic pathway intermediates of glycolysis or pathway intermediates of glycolysis or Kreb’s cycleKreb’s cycle

Once made Once made protein synthesis on protein synthesis on ribosomes can ensue.ribosomes can ensue.