5- Microbial Metabolism

See Table 5.2 for some cofactors

(protein)

(organic)

What catalysts (eg: enzymes) do

(Enzyme is NOT used up)

How do enzymes work?

optimum optimum

competitive inhibition

Non-competitive inhibition

Some older enzyme names don’t follow the modern rules: trypsin, lysozyme, etc.

In many biological redox reactions: electrons are passed on as part of H atoms

Substrate-level phosphorylation

Oxidative- or Photo-phosphorylation

Catabolism

(= degradation)

aerobic

Glycolysis = Embden-Meyerhoff pathway

(see also appendix A)

G3P

Glycolysis (cont.)

2

2

2

2

2

Pentose-phosphate pathway

can use glucose

makes & uses pentoses & other useful substrates for biosynthesis

produces 2 NADPH/ glucose

& 1 ATP (through glycolysis)

(see also App. A-4)

Entner-Doudoroff pathway

uses glucose

produces 1 ATP & 1 NADPH & 1 NADH/glucose

in prokaryotes only

(see also App. A-5)

mitochondria

cytoplasm

Transition/preparatory step/reaction

In mitochondrial matrix

Kreb’s cycle

Citric Acid cycle

TCA cycle

(see also App. A-6)

oxidative -> ETC

phosphorylation -> chemiosmosis

energy

(Eukaryotic about the same)

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)

Some kinds of fermentation

Other kinds of catabolism

Anabolism (= biosynthesis)

Halobacterium

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

Overall:

6 CO2 + 12 H2O

in the presence of lightlight and chlorophyll a yields

C6H12O6 + 6 O2 + 6 H2O

LightLight Dependent Reactions:

12 H2O + 12 NADP+ + 18 ADP + 18 phosphates

with lightlight 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

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

Light Independent Reactions

12 NADPH + 18 ATP + 6 CO2 yields

C6H12O6 (glucose) + 12 NADP+ + 18 ADP

+ 18 phosphates + 6 H2O

(see also Appendix A-7)

In the stroma

Rubisco

Carbon fixation = making sugars

Chemosynthesis:

Using the energy from inorganic chemicals to put together CO2 into sugars

Only some prokaryotes can do

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

Alternative to photosynthesis

eg: hydrogen bacteria, iron bacteria

Other biosyntheses: polysaccharides

Metabolism is

1) integrated and

2) many pathways, not all, are amphibolic

To see more:

http://www.manet.uiuc.edu/pathways.php

http://www.sigmaaldrich.com/etc/medialib/docs/Sigma-Aldrich/General_Information/metabolicpathways_updated_02_07.Par.0001.File.tmp/metabolic_pathways_poster.pdf

http://www.expasy.ch/cgi-bin/show_thumbnails.pl

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