metabolism & fuel growth 6

8/9/2019 Metabolism & Fuel Growth 6

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Metabolism:


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Products of Microbial Metabolism


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ImportantCons

equences

ofM

icrobialMetabolism

Beer, wine, and other alcoholic beverages. Bread (all of above are mostly products of the yeast

Saccharomyces cerevisiae).

Products of lactic-acid bacteria (LAB) including sourmilks, various cheeses, half-sour pickles, sauerkraut,

etc. (e.g., ofLactococcus spp. &Lactobacillus spp.).

Organic solvents including acetone (product ofClostridium acetobutylicum), butanol (ditto), and, of

course, ethanol (product ofS. cerevisiae).

Acetic acid (vinegar). Biochemical identification of bacterial species. Unique (e.g., not found in animals) targets for

antimicrobial action.

Disease (e.g., dental caries).


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Metabolis

m=

Cata

bolism+

A

nabolism

sum = metabolism


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Bioener

getics(s

eeFig.

6.3

)

More generally,chemoheterotrophs.

More generally,

photoautotrophs (orjust autotrophs).

More generally, sun or

reduced inorganic

chemicals (ocean vents).

Note that bacteria

dont have

mitochondria:

aerobic bacteria

are mitochondria!

E.g., glucose


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MetabolismT

erms&Conc

epts

Metabolic pathway = highly evolved intracellularsequence of chemical reactions.

Each step of a metabolic pathway usually isenzymatically catalyzed (and enzymes are proteins).

Substrates are molecules that enter intoenzymatically catalyzed reactions.

Products are what substrates are enzymaticallyconverted into.

Enzymes typically are very precise in terms of whatsubstrates they will accept (often no more than one

specific chemical) and they will convert a substrateinto (often no more than one specific chemical).

Precursor molecules are found at the start ofmetabolic pathways.

Intermediate molecules are found within metabolicpathways.

End products are the molecules ultimately producedby a given metabolic pathway.


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Chemical Energetics

How cellsburn glucose.


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Enzym

eTerms&Concepts

Enzyme names generally are indicated by an -ase ending, e.g., dehydrogenase (lysozyme is

exception).

Enzymes have active sites (a.k.a., catalyticsites).

Cofactors are non-protein components ofenzymes; they can be organic or inorganic.

Coenzymes are organic cofactors; they generallyare carriers of other molecules or ions.

NAD+ for example is a coenzyme.


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Ezym

ewith

Cofacto

r


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Environment Impact on Enzyme Activity


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Enyzmatic Inhibition


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Variation on Metabolic Pathways


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Variation on Metabolic Pathways

Glycolysis is a catabolic pathway.

Krebs citric acid

cycle is a cyclic

catabolic pathway.E.g., ATP, CO2,

and NADH.


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ATP Energy Currency of Cells


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ATP, ADP, and Metabolism


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Oxidation-Reduction (Redox)


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Note NAD+

(not NAD).

Note that 2 hydrogen ions are

removed along with the 2

electrons (only one H+ ends up

attached to NAD+, hence thecharge change).


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Overview

ofM

etabolism


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Glycolysis(seeFig.6.

14)

AnEnzymeandCoenzymeMediatedCatabolicP

athway

Glucose

Pyruvate

NAD+

ATP

ATP

NADH


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Glycolysis(seeFig.6.1

4)


athway


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Glycolysis(seeFig.6.1

4)


athway

Glucose

Pyruvate

NAD+

ATP

ATP

NADH


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RegenerationofNAD+


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RegenerationofNAD+

Glycolysis

Pyruvate

(2e-)

E.g., see Fig.

6.17-6.19(6.16-6.18)


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RegenerationofNAD+

Glycolysis

Pyruvate

(2e-)

above is why

aerobes need O2


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Lactic

AcidFermentation

(seeFig.

6.2

0)

Glycolysis


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Etha

nolFerm

entation

(seeFig.

6.2

0)

Glycolysis

Beer

Bread


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SimpleFermentat

ionPathw

ays


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Mixed-Acid Fermentation

This is why we Fart!


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OtherFermentationPathw

ays


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OtherFermentationPathw

ays

Swiss cheese.

Beer, wine,

bread.

Flatulence!

our own

muscles.


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Anaerobic Respiration

employs an

inorganicmolecule other

than O2 as aterminal

electron

acceptor.


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HydrolyticE

nzymes

Amylases = enzmes that hydrolyze starches to theirconstituent glucoser subunits.

Disaccharidases = enzymes that hydrolyzedissacharides to constituent monosaccharides.

-galactisidase is the most famous of disaccharidases; itbreaks down the sugar lactose (into galactose and glucose).

Lipases = enzymes that hydrolyze fats (into glycerol orand fatty acids).

Proteases = enzymes that break down proteins. Deaminases = enzymes that remove amino groups from

individual amino acids.

The resulting products can be used as alternatives toglucose as carbon and energy sources.

Chemolithotrophs (a.k.a., chemoautotrophs) utilizesubstances other than organic compounds as energysources and get their organic carbon from CO

2.

metabolism & fuel growth 6

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