Metabolic Pathways

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Metabolic Pathways

• Overview of metabolism pathways
• - Catabolism - Anabolism
• - Bioenergetics
• - Important metabolic pathways
• - Catabolism
• - Glucose catabolism
• - aerobic pathway
• - anaerobic pathway
• - Hydrocarbon
• - Nitrogen compounds
• - Anabolism
• - Photosynthesis
• - Biosynthesis

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Metabolic Pathways
M a complete set of chemical
reactions that occur in living cells, allowing
cells to grow and reproduce, maintain their
structures, and respond to their
environments. Major challenges in bioprocess
development To select an organism that can
efficiently make a given product or digest
wastes in the Environment. It is important to
understand the metabolic pathways.
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Metabolic Pathways
- Overview of metabolism pathways Metabolism can
be subdivided by - C
The intracellular process of degrading a compound
into smaller and simpler products and generating
energy. Glucose to CO2, and H2O, protein to
amino acids. - A the
synthesis of more complex compounds and requires
energy. Synthesis of small molecules (amino
acids, nucleotides, fatty acids and sugars) and
complex compounds (glycan (polysaccharide), DNA,
RNA, and lipids.)
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Major Metabolic Pathways in a Bacterial Cell
(M.Shuler, 2002)
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Metabolic Pathways

• Bioenergetics

Sunlight
Photosynthesis by autotrophs CO2 H2O ?
carbohydrates
Autotrophs or heterotrophs
Catabolism generating energy, e.g ATP
Anabolism requiring energy
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Metabolic Pathways

• Bioenergetics
• - Energy is mainly stored or transferred by
  adenosine triphosphate (ATP).
• Other energy carrying compounds include GTP,
  UTP and CTP.

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Metabolic Pathways

• Bioenergetics
• - Reducing power supply hydrogen atom in
  biosynthesis.
• Nicotinamide Adenine Dinucleotide (NADH)
• Flavin Adenine Dinucleotide (FADH2)
• NADH and FADH2 are major electron carriers in
  the oxidation of fuel molecules and for ATP
  generation.
• Nicotinamide Adenine Dinucleotide Phosphate
  (NADPH).
• major electron donor in reductive biosynthesis,
  e.g photosynthesis

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Nicotinamide Adenine Dinucleotide (NAD)
2e- , H
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Flavin Adenine Dinucleotide (FAD)
2 electrons
Isoalloxazine ring
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Nicotinamide Adenine Dinucleotide Phosphate
(NADP)
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Review of Metabolism Pathwayshttp//www.genome.j
p/kegg/pathway/map/map01100.htmlGlucose
metabolism is the centre of the cell metabolism
pathways
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Glucose Catabolism
Glucose
Glycolysis or Embden-Meyerhof-Parnas (EMP)
Anaerobic metabolism
Aerobic metabolism
Fermentation ethanol, acetic acid, lactate.
Tricarboxylic acid (TCA) or (Krebs) or (Citric
acid cycle)
Oxidative phosphorylation
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Glucose CatabolismGlycolysis

• http//www.science.smith.edu/departments/Biology/B
  io231/glycolysis.html

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Glucose CatabolismGlycolysis

• Glycolysis or Embden-Meyerhof-Parnas (EMP)
• Breakdown of a molecule of g to
  two pyruvate molecules.
• - Each pathway is catalyzed by particular
  enzyme(s)
• - Generating 2 ATP, 2 NADH and 2
  pyruvate (Key Metabolite).
• - Taking place in cytoplasm

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(No Transcript)
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Glycolysis (EPM)
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Glucose CatabolismGlycolysis

• The overall reaction in glycolysis is
• Glucose 2ADP 2 NAD 2 Pi ?2 pyruvate
• 2 ATP 2 (NADH H)
• Produce
• - e
• - Key metabolite pyruvate

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Glucose Catabolism
Glucose
Glycolysis or Embden-Meyerhof-Parnas (EMP)
Anaerobic metabolism
Aerobic metabolism
Fermentation ethanol, acetic acid, lactate.
Tricarboxylic acid (TCA) or (Krebs) or (Citric
acid cycle)
Oxidative phosphorylation
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Glucose CatabolismKrebs, Tricarboxylic Acid
(TCA), or Citric Acid Cycle

• Under a conditions
• Taking place
• - in mitochondria in eucaryotes
• - associated with membrane-bound enzymes in
  procaryotes
• Pyruvate produced in glycolysis (EMP) pathway
  transfer its reducing power to NAD.

http//www.science.smith.edu/departments/Biology/B
io231/krebs.html
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Citric Acid Cycle
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Glucose CatabolismCitric Acid Cycle

• The overall reaction of TCA cycle
• acetyl-CoA 3 NAD FAD Pi 2H2O ? CoA
  3(NADH H) FADH2GTP 2CO2
• Intermediate products such as oxylacetate and
  aketoglutarate are used as precursors for the
  synthesis of certain amino acids.
• The reducing power (NADH H and FADH2) is used
  for biosynthesis pathway or for ATP generation
  through the electron transport chain.

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Glucose Catabolism
Glucose
Glycolysis or Embden-Meyerhof-Parnas (EMP)
Anaerobic metabolism
Aerobic metabolism
Fermentation ethanol, acetic acid, lactate.
Tricarboxylic acid (TCA) or (Krebs) or (Citric
acid cycle)
Respiratory chain Oxidative phosphorylation
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Glucose CatabolismRespiratory Chain-Oxidative
Phosphorylation

• Oxidative Phosphorylation is the electron
  transport chain that forms ATP as electrons are
  transferred from NADH or FADH2 to o
  by a series of electron carriers (L. Stryer,
  1988)
• - electron acceptor oxygen (aerobic condition)
• - generate ATP, H2O
• - from NADH or FADH2
• Taking place in mitochondria in eucaryotes
• or in cytoplasmic membrane in procaryotes

http//www.brookscole.com/chemistry_d/templates/st
udent_resources/shared_resources/animations/oxidat
ive/oxidativephosphorylation.html
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Glucose CatabolismOxidative Phosphorylation

• In the process of Oxidative Phosphorylation
• In eucaryotes
• NADH H 3 ATP
• FADH2 2 ATP
• In procaryotes
• NADH H 2 ATP
• FADH2 ATP

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Glucose Aerobic CatabolismReaction Summary

• EMP (glycolysis)
• Glucose 2ADP 2 NAD 2 Pi ?2 pyruvate 2
  ATP 2 (NADH H)
• Entry of pyruvate
• 2pyruvate 2NAD 2CoA-SH ?2 acetyl-CoA
  2CO2 2(NADH H)
• TCA cycle
• 2acetyl-CoA 6 NAD 2FAD 2GDP 2Pi 4H2O ?
  2CoA 6(NADH H) 2FADH22GTP (ATP)
  4CO2
• Oxidative Phosphorylation
• In eucaryotes
• EMP 2 NADH ? 2 FADH2 ? 4 ATP (glycerol
  phosphate shuttle)
• Entry of pyruvate and TCA 8 NADH ? 24 ATP
• TCA 2FADH2 ? 4 ATP
• The overall reaction
• Glucose 6O2 36ADP 36 Pi ? 6 CO2 6 H2O
  36 ATP

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Glucose Catabolism
Glucose
Glycolysis or Embden-Meyerhof-Parnas (EMP)
Anaerobic metabolism
Aerobic metabolism
Fermentation ethanol, acetic acid, lactate.
Tricarboxylic acid (TCA) or (Krebs) or (Citric
acid cycle)
Respiratory chain Oxidative phosphorylation
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Glucose Anaerobic Catabolism
Glycolysis (EMP)
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Hydrocarbon Catabolism

• Hydrocarbon C H
• - Aliaphatic hydrocarbon
• e.g. octane, C8H18
• polyethylene HCCH-
• - Aromatic hydrocarbon
• naphthalene
• Metabolism of hydrocarbon
• - Requires oxygen
• - Hydrocarbons are converted to acetyl-CoA which
  is metabolized by TCA cycle.
• - Challenges low solubility in aqueous
  solution.
• available microorganisms are limited
• Pseudomonas, Mycobacteria

naphthalene
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Nitrogen Compounds Catabolism
Nitrogen compounds can be used for C, N and
energy sources Proteins ? peptides ? amino
acids ? converted to other amino acids or organic
acids and ammonia by deamination. - organic
acids acetyl-CoA into TCA cycle, lipids -
amino acids proteins, other amino acids or enter
TCA cycle - ammonium amino acid, protein,
nucleic acids Nucleic acids ?
ribose/deoxyribose, phosphoric acid and
purine/pyrimidine - sugar glycolysis and
TCA - Phosphoric acid ATP, lipids, nucleic
acids - bases nucleic acids, urea, acetic acids
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Photosynthesis
Glycolysis and TCA
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Overview of Biosynthesis

• Pentose-phosphate pathway (hexo-monophosphate
  pathway (HMP)
• convert glucose-6-phosphate into a carbon
  skeletons of C3 C7 .
• Polysaccharides glycan, glycogen
• gluconeogenesis
• Lipids
• Proteins
• Nucleic acids (DNAs, RNAs)

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5
3
4
6
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Summary of Metabolism Pathways

• Metabolism
• - catabolism ATP, C skeleton for further
  biosynthesis
• - anabolism biosynthesis requiring energy
• Bioenergetics
• - energy storage and carrier ATP
• - Reducing power carriers NADH, NADPH, FADH

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Summary of Metabolism Pathways

• Glucose catabolism

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Summary of Metabolism Pathways

• Nitrogen compound catabolism
• Hydrocarbon catabolism
• Photosynthesis
• Biosynthesis