Insecticides Flashcards
characteristics of inorganic insectisides
- do not have to synthesize; 2. “original insecticides”; 3. do not contain carbon 4. stable, water soluble
characteristics of organochlorines
first synthetic organic pesticide; typically highly persistent; mostly phased out; broad-spectrum insecticidal activity
mechanism of action of sulfur?
mitochondrial electron transport inhibitor; reduced form (H2S) inhibits cytochrome oxidase–>attaches to iron in heme–>competes for O2
arsenic general info
used as a compound with Cu, called paris green; could combine with oxygen to create arsenites (AsO2)/As(III); or arsenates (As)O4/As(IV);
what was As used to treat?
wood, fruits, veg, has broad insecticidal activity (targets: Colorado potato beetle, apple maggots, moth)
how is As poisonous?
a stomach poison, toxic to mammals; caustic if topically exposed; both As (III) and (IV) are proteotoxic, and cause protein coagulation/pptation, b disrupting secondary protein structure; can lead to DNA damage, improper repair, etc
how does As(III) affect the cell?
has high affinity for thiol/sulfhydryl groups, bind to tissue proteins, inactivate;
How does As(IV) affect the cell?
chemical analog of phosphate, inihibits ATP synthesis, uncouples oxphos
As mech of action?
ox phos; lipoic acid and CoA in CAC have lots of thiol groups, so As(III) will target them heavily; without CAC, there is no NADH + H, so no e’s for chemiosmotic gradient, and no NAD; as well, lack of repair for ox stress; As(IV) acts as a Pi analogue, so it outcompetes actual Pi for ADP (no ATP production);
uses of mercury?
with As it could treat lice; mercuric chloride used in households and agriculture against pests; mainly a fungicides;
Mercury mech of action?
interacts with thiol groups on prteins, like As(III), but less specifically; Hg2+ forms a complex with two S molecules, breking protein disulfide bonds (unfolds prots)
uses for Boric Acid (H3BO4)?
targets cockroaches and ants
Boric acid is so incredibly toxic it is used as a reference in soil tox with plants and invertebrates
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mech of action of boric acid?
stomach poison; absorbed through insect cuticle; disrupts integrity of cuticle–>bug can’t keep water balance, dessicates
organochlorine general info
chlorinated diphenyl aliphatic structure; resistant to degradation (esp the Cl-C bond); long-lasting, residula; effects; extremely lipophilic
what is DDT and what does it stand for?
dichlorodiphenyltrichloroethane; a popular insecticide, because it is inexpensive, persistent, and easily applied
DDT general info?
lipophilic; bioaccumulative and biomagnifies up the food chain; persistent; ubiquitous
mech of ACUTE action of DDT?
attacks K channels and Na channels; K cannot move through channel, prevents closure of Na channels (makes membrane leaky); increased binding of Ca to calmodulin, so increased release of NTs; inhibits Na/K and Ca ATPase; since channels aren’t working, conc grad can’t be restored–>RMP never reached; truncation of genes
mech of chronic action of DDT?
endocrine disruption; DDT–> DDE, which is the main toxicant of chronic toxicity; DDE is stable, binds to and activates estrogen receptor (weak agonist); binds to, but does not activate androgen receptor–>leads to AR degradation and reduced androgenic gene expression (has feminizing effects)
what is methoxychlor?
“DDT substitute/replacement”; has insecticidal mech similar to DDT/E;
use of methoxychlor
used for fruit/shade trees; livestock, soil, structures;
advantage of methoxychlor?
less persistent than DDT, as it is more readily metabolized
disadvantage of methoxychlor?
also has estrogenic/anti-androgenic effects like DDE via receptors; these effects have been found to be epigenetic in rodents–>persist through the generations
