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8- Microbial Metabolism

Metabolism

ATP / ADP / AMP

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(See Table 8.2 for some cofactors)

Enzyme structure simple non-protein: ribozyme

examples of Holoenzymes

What catalysts do

(eg: enzymes)

Energy released

(Enzyme is NOT used up)

substrates

products

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optimum optimum

Affecting enzyme function

Inhibition

(allosteric site)

Metabolic pathway control by feedback inhibition

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Metabolic pathway control by gene expression

Redox reactions

In many biological redox reactions:

electrons are usually passed along as part of H atoms

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Substrate-level phosphorylation

Oxidative- or Photo-phosphorylation

Glucose Catabolism

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Glycolysis = Embden-Meyerhoff pathway

Glycolysis (cont.) (occurs in cytoplasm)

Energy-investment stage

Energy-conserving stage

Glycolysis alternative:

Pentose-phosphate pathway

can use glucose

makes & uses pentoses & other useful substrates for biosynthesis

produces 2 NADPH/ glucose & 1 ATP (through glycolysis)

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Glycolysis alternative:

Entner-Doudoroff pathway

uses glucose

produces 1 ATP & 1 NADPH & 1 NADH/glucose

in prokaryotes only

Fate of pyruvate

Kreb’s cycle/

Citric Acid cycle/

TCA cycle

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Transition/preparatory step reaction In mitochondrial matrix

energy

oxidative -> ETC

phosphorylation -> chemiosmosis

Electron Transport Chain/System

Chemiosmosis

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Energy summary for aerobic respiration

Anaerobic Respiration: different final electron acceptor

acceptor product

nitrate (NO3-) -> nitrite (NO2

-)

-> nitrous oxide (N2O)

-> nitrogen gas (N2)

(eg: Pseudomonas, Bacillus)

sulfate (SO42-) -> hydrogen sulfide (H2S)

(eg: Desulfovibrio)

carbonate (CO3-) -> methane (CH4)

(eg: Methanogenium)

homolactic alcoholic

Fermentation ≠ Anaerobic Respiration

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Fermentation: others

Other kinds of catabolism

Anabolism (= biosynthesis)

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Halobacterium (Archaea)

Photosynthesis group PS pigments(s) 1) purple S bacteriochlorophylls a or b 2) purple non-S bacteriochlorophylls a or b ---------------------------------------------------------- 3) green S bacteriochlorophylls a + c,

d, or e 4) green non-S bacteriochlorophylls a + c ---------------------------------------------------------- 5) heliobacteria bacteriochlorophyll g ---------------------------------------------------------- 6) Halobacterium bacteriorhodopsin ---------------------------------------------------------- 7) cyanobacteria chlorophyll a + phycobilins ---------------------------------------------------------- 8) PS-protists chlorophyll a + various 9) almost all chlorophyll a + b land plants

Chloroplast anatomy & the 2 sets of reactions

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Overall:

6 CO2 + 12 H2O

in the presence of light & chlorophyll a yields

C6H12O6 + 6 O2 + 6 H2O

Light Dependent Reactions:

12 H2O + 12 NADP+ + 18 ADP + 18 phosphates with light and chlorophyll a yields:

6 O2 + 12 NADPH + 18 ATP

Light Independent Reactions:

12 NADPH + 18 ATP + 6 CO2 yields:

C6H12O6 (glucose) + 12 NADP+ + 18 ADP + 18 phosphates + 6 H2O

Light Dependent Reactions

chloroplast

In eukaryotic chloroplasts & cyanobacteria there are 2 kinds of photosystems: I & II

Other light-harvesting pigments

Light-Dep. Reactions: Non-cyclic photophosphorylation

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Light-Dep. Reactions: Cyclic photophosphorylation

Carbon fixation = making sugars

From non-cyclic

From cyclic

Chemosynthesis: Using the energy from inorganic chemicals to build sugars from CO2; an alternative to photosynthesis.

Only some prokaryotes can do this.

Is done where there is no light, but can be done where there is light.

One example: sulfur bacteria

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Metabolism is

1) integrated and

2) many pathways, not all, are amphibolic

To see more about metabolism (including animations):

IUBMB-Nicholson Metabolic Maps, Minimaps & Animaps http://www.iubmb-nicholson.org/

More advanced

http://www.genome.jp/kegg/pathway.html