6. microbial metabolism.220.io

7/29/2019 6. Microbial Metabolism.220.IO

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BIO 220 INSTRUCTORS OUTLINE

Microbial Metabolism

Terms:

Enzyme

Active Site

Allosteric Site

Allosteric Activation

Allosteric Inhibition

Role of enzymes increasing rate of reactions

Sequester substrates

Create microenvironment

Lower Activation Energy (EA) of reaction

Enzymes do not change G of reaction

Enzymes remain chemically unchanged upon completion of reaction

Substrate

End Product

Co-Enzyme

Co-Factor

Metabolism

Catabolism

Anabolism

Gibbs Free Energy

Endergonic reaction

Exergonic reaction

Activation Energy (EA)

Hydrolysis reaction

Condensation reaction

Redox reactions

Oxidation

Reduction

Short term sources of energy

Long term sources of energy

Chemoorganotrophs

Aerobic Respiration (O2 as terminal electron acceptor)


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Anaerobic Respiration (Inorganic ions as terminal electron acceptor; NO32-

,

Hg2+

, etc.)

Fermentation (endogenous organic molecule as terminal electron acceptor)

C6H12O6 + 6O2 -----> 6 CO2 + 6 H20

Glycolysis

Citric Acid Cycle

Electron Transport

Chemiosmosis

Redox Potential

The difference in energy from electron donor to terminal electron acceptor

Compare O2 vs NO32-

Substrate Level Phosphorylation

Synthesis of ATP using phosphorylated organic molecule as donor

Glycolysis

Citric Acid Cycle

Oxidative Phosphorylation

Phosphorylation of ADP with inorganic phosphate to produce ATP

Catalyzed by ATP SynthaseEnzyme located in Plasma Membrane

Reaction occurs on cytoplasmic surface

Energy for reaction provided by Proton Motive Force

Glycolysis

Glucose -> 2 Pyruvate

Occurs in cytoplasm

Series of 10 reactions

1

st

5 reactions- energy investment2

nd5 reactions- energy payoff

2 net ATP yield via Substrate Level Phosphorylation

NADH generated as carbon is oxidized

Decarboxylation of Pyruvate yields CO2 + Acetlyl-CoA + NADH

Citric Acid Cycle


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Acetyl group of Acetyl-CoA donated to a series of redox reactions

Ultimate product is CO2Oxidation of carbon produces NADH and FADH2

ATP via Substrate level Phosphorylation

Occurs in cytoplasm + 1 enzyme (Succinate Dehydrogenase) on plasma

membrane

Electron Transport Chain

Series of enzymes located in Plasma Membrane

Oxidizes NADH and FADH2 generated during Glycolysis, Citric Acid Cycle

Ultimately donates electrons to oxygen forming water

Decreasing Free Energy and increasing Electronegativity keep electron flow

unidirectional

Some enzymes accept electrons + hydrogen

Hydrogen ions translocated unidirectionally across membrane

Some carriers accept electrons only

Proton Motive Force

Chemical and electrical component

Used for Motility, Transport, ATP Synthesis via Oxidative Phosphorylation

Chemiosmosis

Link between Electron Transport Chain and Oxidative Phosphorylation

Uncouplers- 2,4 Dinitrophenol

Inhibitors electron transport

Cyanide, Carbon MonoxideInhibitor of ATP Synthase- Oligomycin

Anaerobic Respiration

Nitrate Reduction

Utilizes Glycolysis, Citric Acid Cycle, Electron Transport Chain, ATP Synthase

Energy yield slightly less than aerobic respiration due to differences in redox

potential

Sulfate ReductionH2 Electron donor, oxidized by Hydrogenase

Adenosine phosphosulphate + SO32-

act as electron acceptors

ATP Synthase

See figure 17.39

Fermentation


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Reduction of Pyruvate or other compounds to regenerate NAD+

Biosynthestic Pathways

Glycolysis, Citric Acid Cycle pathways contain precursors to nucleic acids, amino acids

See figure 5.25d, 5.26

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