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Microbiology
Microbial Metabolism II
Catabolism & Anabolism
Ching-Tsan Huang (黃慶璨)
Office: Room 111, Agronomy Hall
Tel: (02) 33664454
E-mail: cthuang@ntu.edu.tw
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Anabolism
Use of Energy in Biosynthesis
Turnover
Carefully regulated
Catabolism
Energy Release and Conservation
Provide materials for biosynthesis
Amphibolic pathways
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Amphibolic Pathways
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Source of Energy for Microorganisms
Phototrophy
Chemoorganotrophy Chemolithotrophy
Chemical Energy
Work
Chemoorganotrophic Catabolisn
Respiration
Aerobic
Respiration
Anaerobic
Respiration
Fermentation
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Chemoorganotrophic Metabolism
Aerobic respiration
using oxygen as exogenous electron acceptor
yields large amount of energy, primarily by electron
transport activity
Anaerobic respiration
using molecules other than oxygen as exogenous
electron acceptors
yields large amount of energy, primarily by electron
transport activity
Fermentation
using endogenous electron acceptor
often occurs under anaerobic conditions
limited energy made available
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Overview of Aerobic Catabolism
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Carbohydrate Catabolism: GlucoseÆPyruvate
Glycolysis
Most common
Also called EmbdenMeyerhof pathway
Occurs in cytoplasmic
matrix of both
procaryotes and
eucaryotes
Generation of NADH
ATP synthesis via
substrate-level
phosphorylation
Glucose + 2 ADP + 2 Pi + 2 NAD+
2 Pyruvate + 2 ATP + 2 NADH + 2 H+
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Carbohydrate Catabolism: GlucoseÆPyruvate
Pentose Phosphate
Pathway
provide NADPH as
source of electrons
4-carbon sugar for
aromatic amino acid
synthesis and 5-carbon
sugar for nucleic acid
synthesis and CO2
acceptor
Aerobic or anaerobic
3 Glucose-6-P + 6 NADP+ + 3 H2O
2 Fructose-6-P + Glyceraldehyde-3-P + 3 CO2 + 6 NADPH + 6 H+
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Carbohydrate Catabolism: PyruvateÆCO2
Aerobic
Use O2 as eacceptor
TCA (tricaboxylic
acid) cycle or
Citric acid cycle or
Kreb’s cycle
Function
Provide carbon
skeletons for use
in biosynthesis
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Electron Transport
Electron transport chain
in the inner membrane of the mitochondrion
in the bacterial plasma membrane
Electron donors:
NADH (3 ATPs)
FADH2 (2 ATPs)
Electron acceptor:
Oxidative
phosphorylation:
process by which
energy from electron
transport is used to
make ATP
Wolinella succinogenes is a nonfermenting bacterium with fumurate as
its sole carbon source. It undergoes anaerobic fumerate respiration.
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Carbohydrate Catabolism: Glucose Æ CO2
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Fermentations
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Carbohydrate Catabolism: PyruvateÆCO2
Anaerobic
Fermentation
No exogeneous eacceptor
Use organic
molecules as eacceptor
ATP formed by
substrate-level
phosphorylation
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Lipid Catabolism
Lipid
Fatty acid + Glycerol
Fatty acid β-oxidation
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Protein and Amino Acid Catabolism
Protease
Hydrolysis of protein to amino acids
Deamination
Often occurs by transamination
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Principles Governing Biosynthesis
Macromolecules are synthesized from limited number of
simple structural units (monomers)
Many enzymes used for both catabolism and anabolism
Catabolic and anabolic pathways are not identical,
despite sharing many enzymes
Breakdown of ATP coupled to certain reactions in
biosynthetic pathways
Catabolic and anabolic pathways use different cofactors
Large assemblies (e.g., ribosomes) form spontaneously
from macromolecules by self-assembly
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Energy Trapping: Photosynthesis
Anoxygenic
Oxygenic
Light reaction
light energy is trapped and converted to chemical
energy
Dark reaction
reduce or fix CO2 and synthesize cell constituents
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Light Reaction
Eucaryotes &
Cyanobacteria
Green & Purple
Bacteria
PMF
Reversed
e- flow
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Photosynthetic Fixation of CO2
Autotrophs obtain energy by
trapping light during photosynthesis or by oxidizing or
reduced inorganic e- donors
Calvin, Calvin-Benson,
reductive pentose
phosphoraltion cycle
in eucaryotes, occurs in
stroma of chloroplast
in cyanobacteria, some
nitrifying bacteria occur in
carboxysomes
Carboxylation
Reduction
6 RuBP + 6 CO2
12 PGA
6 RuBP + Fructose 6-P
Regeneration
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Synthesis of Pyruvate to Glucose
Gluconeogenesis: Heterotrophs synthesize sugars
by reducing organic molecules
Glucoeogenesis
Glycolysis
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Synthesis of Sugars and Polysaccharides
Gluconeogenesis
synthesize glucose and fructose from
noncarbohydrate precursors
Sugar nucleoside diphosphates
synthesis of other sugars , polysaccharides,
and bacterial cell walls
ATP + glucose 1-P →
ADP-glucose + PPi
(glucose)n + ADP-glucose →
(glucose)n+1 + ADP
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Synthesis of Amino Acids
Precursor metabolites used as starting substrates
carbon skeleton is remodeled
amino group and sometimes sulfur are added
Nitrogen addition to carbon skeleton is important
potential sources of nitrogen: ammonia, nitrate, or
nitrogen
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Synthesis of Amino Acids
Phosphoenolpyruvate
Oxaloacetate
α-ketoglutarate
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Lipid Synthesis
Fatty acid synthesis
ACP: acryl carrier protein
Triacrylglycerols & phospholipids