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Environmental Toxicology > Chapter 5 - Biotransformation > Flashcards

Chapter 5 - Biotransformation Flashcards

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1
Q

microbial biodegradation of pollutants

A
  • disposal of organic pollutants
  • bioremediation
  • microbial enzymes in bioremediation
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2
Q

how were organic wastes tradiitionally disposed of?

A

digging a hole and filling the hole with waste products

difficult to sustain

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3
Q

transfer of organic contaminats from the soil/sediment to another medium (ex. soil to air or soil to water)

A

physical separation treatment technologies

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4
Q

what was once considered the standard for destruction/removal of organic pollutants?

A

incineration by thermal oxidation

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5
Q

what issues lead to a greater focus on biological treatment technolgies?

A
  • physical separation treatment technologies
  • inceneration
  • chemical decomposition

all inefficient

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6
Q

microorganims-mediated transformation or degradation of contaminants into non-hazardous or less-hazardous substances

A

bioremediation

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7
Q

what is considered effetive bioremediation

A

microorganisms enzymatically attack the pollutants and convert them to harmless products

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8
Q

what do bacteria rely on for the degradation of organic pollutants?

A

various intracellular/extracellular enzymes

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9
Q

what are the three classification of bioremediation?

A

1) biotransformation
2) biodegradation
3) mineralization

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10
Q

the alteration of contaminant molecules into less or nonhazardous molecules

A

biotransformation

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11
Q

the breakdown of organic substances in smaller organic or inorganic molecules

A

biodegradation

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12
Q

the complete biodegradation of organic materials into inorganic constituents such as CO2 or H2O4

A

mineralization

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13
Q

biological catalysts that facilitate the conversion of substrates into products by providing favorable conditions that lower the activation energy of the reaction

A

enzymes

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14
Q

what are the six major groups of enzymes?

A

1) oxioreductases
2) transferases
3) hydrolases
4) lysases
5) isomerases
6) ligases (synthetases)

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15
Q

catalyze the trasfer of electrons/protons from a donor to an acceptor

A

oxioreductases

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16
Q

catalyze the transfer of a functional group from a donor to an acceptor

A

transferases

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17
Q

facilitate the cleavage of C-C, C-O, C-N, and other bonds by water

A

hydrolases

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18
Q

catalyze the cleavage of C-C, C-O, and C-N by elimination

A

lyases

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19
Q

facilitate geometric or structural rearrangement

A

isomerases

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20
Q

catalyze the joining of two molecules

A

ligases (synthetases)

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21
Q

mediates detoxification of toxic organic compounds through oxidative coupling

A

microbial oxioreductases

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22
Q

Microbes assist in the transfer of electrons from a reduced organic substrate (donor) to another chemical compound (acceptor).

A

microbial oxioreductases

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23
Q

have a major role in the metabolism of organic compounds
* increase their reactivity or water solubility
* bring about cleavage of aromatic ring
* oxidize substrates through the transferring oxygen from molecular oxygen
* broad substrate range /active against a wide range of compounds, including the chlorinated aliphatics

A

microbial oxygenases

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24
Q

what are the two categorized of microbial oxygenases?

A

1) monooxygenases
2) dioxygenases

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25
* incorporates 1 atom of oxygen molecule into a substrate * catalyzes various aromatic and aliphatic compounds' desulfurization, dehalogenation, denitrification, ammonification, hydroxylation, biotransformation, and biodegradation
monooxygenases
26
how do monoxygenases act in a mechanism?
adds one oxygen atom to an aromatic ring forming a hydroxyl group
27
what is an example of a monoxygenase reaction?
n-Alkane to primary alcohol
28
* introduces 2 oxygen atoms into a substrate * primarily oxidizes aromatic compounds * found in soil bacteria and involved in the transformation of aromatic precursors
dioxygenases
29
how do dioxygenases act in a mechanism?
adds two oxygen atoms to a ring. creates two hydroxyl groups on the aromatic ring. ring cleavage dioxygenase reacts with the hydroxyl groups and breaks the rings
30
what is the difference between an intradiol cleavage and an extradiol cleavage?
intradiol: two oxygen atoms react with both hydroxyl groups extradiol: one oxygen atoms reacts with the hydroxul group and one breaks another C bond
31
family of oxidases that catalyzes the oxidation of a wide range of reduced phenolic aromatic substrates with molecular oxygen
microbial laccases
32
catalyzes polymerization processes * direct degradation * polymerized pollutants often become insoluble/immobilized = easier removal by sedimentation/filtration/absorption
microbial laccases
33
what is the general mechanism for phenol oxidation by laccases?
removes hydrogen from one hydroxyl group; removes another hydrogen from the other hydroxul group | polymerization
34
Used for the decomposition of pollutants, textile dye degradation, lignin degradation, dye decolorization, and sewage treatment * wastewater treatment * Some can oxidize PAHS and transform these into more degradable compounds
microbial peroxidases
35
what is the mechanism for microbial peroxidases?
removes accepts two protons and creates two C=O bonds
36
What mechanism does this represent?
microbial peroxidase
37
distrupts major cheical bonds in toxic molecules * reduces toxicity * catalyzes several related reactions including condensations and alcoholysis
microbial hydrolytic enzymes
38
what are some advantages to microbial hydrolytic enzymes?
* readily available * lack of cofactor * stereoselectivity * tolerate the addition of water-miscible solvents
39
found in bacteria, plant, actinomycetes, and animal cells * catalyzes breakdown or hydrolysis of fats * breaks tryglycerides ester bonds in the presence of water
microbial lipases
40
what is the mechanism for microbial lipases?
removes OCOC17H33 from lipid group in different phases
41
produced by bacteria, archaea, and fungi. degrades lingocellulosic waste ptoduced by forest and agriculture industries
microbial cellulases
42
what are the three groups of cellulases?
1) endoglucanase 2) exoglucanase 3) β-glucosidase
43
creates free chain endes in the hydrolysis process
endoglucanase
44
removes cellobiose units from the free chain ends
exoglucanase
45
hydrolyzes cellobiose to glucose units
β-glucosidase
46
what is the mechanism for microbial cellulases?
breaks off oxygen ester bonds to create individual glucose molecules
47
products of different categories of cellulases
exo: cellobiose endo: oligosaccharides of differing sizes
48
study
49
what is the most commonly used pesticide?
glyphosphate
50
what are the four most common pesticides (2008)?
* glyphosphate * atrazine * acetochlor * metolachlor
51
what are the most common pesticides used in soil?
* linuron * napropamide * chloridazon
52
most common herbicide used in ag, lawn, and garden care
glyphosphate
53
what is the mode of action for glyphosphate?
* inhibits EPSP synthase * shikimic acid
54
modes of resistance for glyphosphate
* sequester in vacuoles * increases expression os ESPS synthase * reduced translocation
55
proposed pathways for oxidation via Aldo-Keto reductase
* EcAKR4-1 * glyphosphate -> glyoxylate * transaminase * glycine * cinnamyl alcohol -> EcAKR4-1 -> cinnamaldehyde | study very hard
56
agricultural herbicide used in home landscapes
atrazine
57
mode of action for atrazine
* inhibits Hill reaction in chloroplasts * plants can no longer produce sugars
58
transformation of atrazine
* Glutathione S-transferase (GST) * Cytochrome P450s14 (P450) | study hard
59
agricultural herbicides used alongside or instead of atrazine
* acetochlor * metolachlor
60
mode of action for acetochlor and metolachlor
* inhibits long-chain fatty acids and gibberellin pathway * inhibits growth of young shoots
61
transformation of metolachlor
1) Phase I - O-demethylation 2) Phase II - GSH conjugation 3) Phase III - vacuolar transport 4) Phase IV - catabolism
62
how does S-metolachlor transform into S-metolachlor GSH?
through the action of GSH. phase I to phase II
63
how is S-metolachlor GSH transported into the vacuole?
ABC transporters. phase III
64
when S-metalochlor GSH enters the vacuole, what transforms it into S-metolachlor CYS-CLY?
peptidase
65
what transforms S-metolachlor CYS-GLY into S-metolachlor CYS?
peptidase
66
mode of action of linuron
* interferes with electron transport of photosystem II * prevents photosynthesis
67
* degradation pathways in plants not well-known * begins with demethylation (P450) in corn, soybean, and crabgrass
linuron
68
primary mode of breakdown for linuron
* N-alkyl hydroxylation in lupine * further oxidastion and conjugation within the plant
69
* mode of action not well understood * agricultural herbicide * inhibits root growth * deradation pathways in plants not well known
napropamide
70
by-products found in tomatoes from napropamide
hexose conjugates * 2-N-ethyl propionamide * 2-N, N-diethyl propionam
71
modes of resistance for napropamide
* translocate out of roots (tomatoes) * extensive root systems
72
mode of action for chloridazon
* interfers with electron transport of photosystem II * prevents photosynthesis
73
plants that chloridazon degrades
* soybean * dwarf bean * cotton * sugar beet
74
in plants, most compounds are stored in ____ or ____ throughout the plant.
lipids; transported
75
most detox pathways invloved what two enzymes?
* GST * Cytochrome 450
76
what are the primary responsibilities for the enzymes GST or cytochrome 450 in detox pathways?
* transform pesticides * breakdown pesticides: encourage enzyme synthesis

Environmental Toxicology (9 decks)

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