Insecticide Penetration

Question 1

Which three types of transport involve movement down a concentration gradient?

Answer 1

• Facilitated diffusion
• Passive diffusion
• Filtration

Question 2

What makes mammalian skin a better barrier against contact insecticides than insects?

Answer 2

Mammals have soft, flexible keratinized skin

Question 3

The outermost layer of the insect integument is _____________

Answer 3

waxy and lipophilic, making it hydrophobic.

Question 4

Most insecticides are what?

Answer 4

Contact poison

Question 5

The efficacy of insecticides is highest for what type of compounds?

Answer 5

Non-polar lipophilic compounds

Question 6

Why is passive diffusion the most common type of movement of insecticides through biological membranes?

Answer 6

because of the lipophilic nature of insecticides and biological membranes

Question 7

The integument is made up of…

Answer 7

Epidermis and cuticle

Question 8

What four factors affect the penetration of insecticides?

Answer 8

• Integument thickness
• Lipid solubility of the insecticide
• Solubility of the insecticide in hemolymph
• The types of cuticular components

Question 9

What three considerations are important for a toxic response to occur?

Answer 9

• Duration of exposure
• Movement across biological membranes
• The toxicant must reach the target site in a sufficient quantity

Question 10

Why more than 99% of the applied active ingredient does not reach the target site?

Answer 10

Processes including penetration, and transport across membranes, among others, contribute to this inefficiency. However, the ability of insects to metabolize toxic foreign compounds might be the single most important factor.

Question 11

What is detoxification?

Answer 11

Detoxification is the ability of insects to convert toxic compounds into non-toxic substances. However, insects do not always detoxify compounds. Often, insects increase the water solubility of toxic compounds so they can be more excretable, which is not necessarily detoxification.

Question 12

What do monooxygenases do?

Answer 12

Monooxygenases insert a single oxygen atom from O2 into xenobiotic molecules.

Question 13

What are Cytochrome P450s?

Answer 13

• Carbon-monoxide-binding pigments of microsomes
• Hemoproteins

Question 14

What are microsomes?

Answer 14

Microsomes refer to the subcellular fraction containing membrane bound enzymes which are imbedded in the endoplasmic reticulum.

Question 15

What do hydrolases yield when they split ester compounds by the addition of water?

Answer 15

• Alcohol
• Acid

Question 16

How do many metabolic reactions alter foreign compounds?

Answer 16

They increase the water solubility of foreign compounds so they can be excreted.

Question 17

Where is cytochrome P450 typically most concentrated in insects?

Answer 17

The digestive tract

Question 18

Many metabolic reactions involve formation of a product that is more toxic than its parent compound. What is this phenomenon called?

Answer 18

Activation

Question 19

What is the primary enzyme system involved in the metabolism of lipophilic xenobiotics in insects?

Answer 19

Cytochrome P450-dependent microsomal monooxygenases

Question 20

Where is the P450 system embedded in the cell?

Answer 20

Endoplasmic reticulum