Chapter 13

Question 1

ch13.q7
What were the main uses of DDT? Explain
why it is no longer used in many developed
countries, and why some developing countries
wish to continue using it.

Answer 1

• Main use = insecticide
• Its very good for stopping air borne illnesses such as malaria (why poor countries want it) but also bio accumulates and bio magnifies in the environment (why it has been banned)

-Birds indirectly incorporate it into their bodies (I think it makes they’re eggs too soft which kills the lil babies)

Question 2

Ch13q8

Explain how DDT functions as an insecticide.

Answer 2

toxic to insects by wedging in nerve channel initiating continuous nerve impulses

In insects, DDT become wedged in the nerve channel that leads out from nerve cell. continuous series of Na+-initiated nerve impulses is produced when the DDT molecule holds open the channel. As a consequence, the muscles twitch constantly exhausting it with convulsions that lead to death.

Question 3

ch13.q10
Explain what is meant by the terms
bioconcentration and bioconcentration factor (BCF).

Answer 3

BCF = indicates degree of chemical residue accumulates in aquatic organisms (usually fish), coincident with ambient concentration of the chemical in water

BCF = [] in organism (mg/kg) / [] in water (mg/L)

Bioconcentration = accumulation of a chemical in an aquatic organism due to uptake from surrounding water

Question 4

ch.13.q11
Explain what is meant by the term
biomagnification and how it differs from
bioconcentration.

Answer 4

Biomagnification = increase in contaminant concentrations in organism up the food chain

bio magnification is looking at the increase from organism eating smaller contaminated whereas bioconcentration is from increases due to taking in contaminant from environment.

Question 5

ch13.q13
Describe one analog of DDT that works in
the same fashion but does not bioaccumulate.

Answer 5

Methoxychlor

• Cl in para position replaced with methoxy group
• More biodegradable and less toxic to mammals

Question 6

ch13.q18
In what way are organophosphate insecticides considered superior to organochlorines as pesticides? In what way are they more dangerous?

Answer 6

superior: Not persistent – decomposes rapidly , within days or weeks. Do not bioaccumulate

Dangerous: Very toxic, linked to impaired neurological development in the fetus and in infants, chronic fatigue syndrome, and Parkinson’s disease.

Question 7

ch13.q27
Write out three examples of hydrolysis
reactions by which pesticides are degraded in the
environment.

Answer 7

1. Most organophosphate insecticides:
2. carbamates are short-lived in the environment since they undergo hydrolysis reactions and decompose to simple, nontoxic products.
3. analogous phenoxy herbicides undergoes a hydrolysis reaction in the environment, degrading the compound to a phenol

Pages: 598, 600 and 613 for reactions