Insecticides

Question 1

characteristics of inorganic insectisides

Answer 1

1. do not have to synthesize; 2. “original insecticides”; 3. do not contain carbon 4. stable, water soluble

Question 2

characteristics of organochlorines

Answer 2

first synthetic organic pesticide; typically highly persistent; mostly phased out; broad-spectrum insecticidal activity

Question 3

mechanism of action of sulfur?

Answer 3

mitochondrial electron transport inhibitor; reduced form (H2S) inhibits cytochrome oxidase–>attaches to iron in heme–>competes for O2

Question 4

arsenic general info

Answer 4

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);

Question 5

what was As used to treat?

Answer 5

wood, fruits, veg, has broad insecticidal activity (targets: Colorado potato beetle, apple maggots, moth)

Question 6

how is As poisonous?

Answer 6

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

Question 7

how does As(III) affect the cell?

Answer 7

has high affinity for thiol/sulfhydryl groups, bind to tissue proteins, inactivate;

Question 8

How does As(IV) affect the cell?

Answer 8

chemical analog of phosphate, inihibits ATP synthesis, uncouples oxphos

Question 9

As mech of action?

Answer 9

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);

Question 10

uses of mercury?

Answer 10

with As it could treat lice; mercuric chloride used in households and agriculture against pests; mainly a fungicides;

Question 11

Mercury mech of action?

Answer 11

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)

Question 12

uses for Boric Acid (H3BO4)?

Answer 12

targets cockroaches and ants

Question 13

Boric acid is so incredibly toxic it is used as a reference in soil tox with plants and invertebrates

Answer 13

ya

Question 14

mech of action of boric acid?

Answer 14

stomach poison; absorbed through insect cuticle; disrupts integrity of cuticle–>bug can’t keep water balance, dessicates

Question 15

organochlorine general info

Answer 15

chlorinated diphenyl aliphatic structure; resistant to degradation (esp the Cl-C bond); long-lasting, residula; effects; extremely lipophilic

Question 16

what is DDT and what does it stand for?

Answer 16

dichlorodiphenyltrichloroethane; a popular insecticide, because it is inexpensive, persistent, and easily applied

Question 17

DDT general info?

Answer 17

lipophilic; bioaccumulative and biomagnifies up the food chain; persistent; ubiquitous

Question 18

mech of ACUTE action of DDT?

Answer 18

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

Question 19

mech of chronic action of DDT?

Answer 19

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)

Question 20

what is methoxychlor?

Answer 20

“DDT substitute/replacement”; has insecticidal mech similar to DDT/E;

Question 21

use of methoxychlor

Answer 21

used for fruit/shade trees; livestock, soil, structures;

Question 22

advantage of methoxychlor?

Answer 22

less persistent than DDT, as it is more readily metabolized

Question 23

disadvantage of methoxychlor?

Answer 23

also has estrogenic/anti-androgenic effects like DDE via receptors; these effects have been found to be epigenetic in rodents–>persist through the generations