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Environmental Toxicology > Chapter 5 - Biotransformation > Flashcards

Chapter 5 - Biotransformation Flashcards

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
Q
  • incorporates 1 atom of oxygen molecule into a substrate
  • catalyzes various aromatic and aliphatic compounds’ desulfurization, dehalogenation, denitrification, ammonification, hydroxylation, biotransformation, and biodegradation
A

monooxygenases

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26
Q

how do monoxygenases act in a mechanism?

A

adds one oxygen atom to an aromatic ring forming a hydroxyl group

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27
Q

what is an example of a monoxygenase reaction?

A

n-Alkane to primary alcohol

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28
Q
  • introduces 2 oxygen atoms into a substrate
  • primarily oxidizes aromatic compounds
  • found in soil bacteria and involved in the transformation of aromatic precursors
A

dioxygenases

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29
Q

how do dioxygenases act in a mechanism?

A

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

intradiolcleavage vs extradiolcleavage
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30
Q

what is the difference between an intradiol cleavage and an extradiol cleavage?

A

intradiol: two oxygen atoms react with both hydroxyl groups
extradiol: one oxygen atoms reacts with the hydroxul group and one breaks another C bond

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31
Q

family of oxidases that catalyzes the oxidation of a wide range of reduced phenolic aromatic substrates with molecular oxygen

A

microbial laccases

32
Q

catalyzes polymerization processes
* direct degradation
* polymerized pollutants often become insoluble/immobilized = easier removal by sedimentation/filtration/absorption

A

microbial laccases

33
Q

what is the general mechanism for phenol oxidation by laccases?

A

removes hydrogen from one hydroxyl group; removes another hydrogen from the other hydroxul group

polymerization

34
Q

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

A

microbial peroxidases

35
Q

what is the mechanism for microbial peroxidases?

A

removes accepts two protons and creates two C=O bonds

36
Q

What mechanism does this represent?

A

microbial peroxidase

37
Q

distrupts major cheical bonds in toxic molecules
* reduces toxicity
* catalyzes several related reactions including condensations and alcoholysis

A

microbial hydrolytic enzymes

38
Q

what are some advantages to microbial hydrolytic enzymes?

A
  • readily available
  • lack of cofactor
  • stereoselectivity
  • tolerate the addition of water-miscible solvents
39
Q

found in bacteria, plant, actinomycetes, and animal cells
* catalyzes breakdown or hydrolysis of fats
* breaks tryglycerides ester bonds in the presence of water

A

microbial lipases

40
Q

what is the mechanism for microbial lipases?

A

removes OCOC17H33 from lipid group in different phases

41
Q

produced by bacteria, archaea, and fungi. degrades lingocellulosic waste ptoduced by forest and agriculture industries

A

microbial cellulases

42
Q

what are the three groups of cellulases?

A

1) endoglucanase
2) exoglucanase
3) β-glucosidase

43
Q

creates free chain endes in the hydrolysis process

A

endoglucanase

44
Q

removes cellobiose units from the free chain ends

A

exoglucanase

45
Q

hydrolyzes cellobiose to glucose units

A

β-glucosidase

46
Q

what is the mechanism for microbial cellulases?

A

breaks off oxygen ester bonds to create individual glucose molecules

47
Q

products of different categories of cellulases

A

exo: cellobiose
endo: oligosaccharides of differing sizes

48
Q

study

A
49
Q

what is the most commonly used pesticide?

A

glyphosphate

50
Q

what are the four most common pesticides (2008)?

A
  • glyphosphate
  • atrazine
  • acetochlor
  • metolachlor
51
Q

what are the most common pesticides used in soil?

A
  • linuron
  • napropamide
  • chloridazon
52
Q

most common herbicide used in ag, lawn, and garden care

A

glyphosphate

53
Q

what is the mode of action for glyphosphate?

A
  • inhibits EPSP synthase
  • shikimic acid
54
Q

modes of resistance for glyphosphate

A
  • sequester in vacuoles
  • increases expression os ESPS synthase
  • reduced translocation
55
Q

proposed pathways for oxidation via Aldo-Keto reductase

A
  • EcAKR4-1
  • glyphosphate -> glyoxylate
  • transaminase
  • glycine
  • cinnamyl alcohol -> EcAKR4-1 -> cinnamaldehyde

study very hard

56
Q

agricultural herbicide used in home landscapes

A

atrazine

57
Q

mode of action for atrazine

A
  • inhibits Hill reaction in chloroplasts
  • plants can no longer produce sugars
58
Q

transformation of atrazine

A
  • Glutathione S-transferase (GST)
  • Cytochrome P450s14 (P450)

study hard

59
Q

agricultural herbicides used alongside or instead of atrazine

A
  • acetochlor
  • metolachlor
60
Q

mode of action for acetochlor and metolachlor

A
  • inhibits long-chain fatty acids and gibberellin pathway
  • inhibits growth of young shoots
61
Q

transformation of metolachlor

A

1) Phase I - O-demethylation
2) Phase II - GSH conjugation
3) Phase III - vacuolar transport
4) Phase IV - catabolism

62
Q

how does S-metolachlor transform into S-metolachlor GSH?

A

through the action of GSH. phase I to phase II

63
Q

how is S-metolachlor GSH transported into the vacuole?

A

ABC transporters. phase III

64
Q

when S-metalochlor GSH enters the vacuole, what transforms it into S-metolachlor CYS-CLY?

A

peptidase

65
Q

what transforms S-metolachlor CYS-GLY into S-metolachlor CYS?

A

peptidase

66
Q

mode of action of linuron

A
  • interferes with electron transport of photosystem II
  • prevents photosynthesis
67
Q
  • degradation pathways in plants not well-known
  • begins with demethylation (P450) in corn, soybean, and crabgrass
A

linuron

68
Q

primary mode of breakdown for linuron

A
  • N-alkyl hydroxylation in lupine
  • further oxidastion and conjugation within the plant
69
Q
  • mode of action not well understood
  • agricultural herbicide
  • inhibits root growth
  • deradation pathways in plants not well known
A

napropamide

70
Q

by-products found in tomatoes from napropamide

A

hexose conjugates
* 2-N-ethyl propionamide
* 2-N, N-diethyl propionam

71
Q

modes of resistance for napropamide

A
  • translocate out of roots (tomatoes)
  • extensive root systems
72
Q

mode of action for chloridazon

A
  • interfers with electron transport of photosystem II
  • prevents photosynthesis
73
Q

plants that chloridazon degrades

A
  • soybean
  • dwarf bean
  • cotton
  • sugar beet
74
Q

in plants, most compounds are stored in ____ or ____ throughout the plant.

A

lipids; transported

75
Q

most detox pathways invloved what two enzymes?

A
  • GST
  • Cytochrome 450
76
Q

what are the primary responsibilities for the enzymes GST or cytochrome 450 in detox pathways?

A
  • transform pesticides
  • breakdown pesticides: encourage enzyme synthesis

Environmental Toxicology (9 decks)

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