Factors Influencing Toxicity

Question 1

type of response depends on many factors

Answer 1

• route of exposure
• endpoints we measure
• duration of study
• properties of the compound
• single compound vs mixture
• half-life of the compound
• excretion rate
• tolerance
• resistance
• genetics

Question 2

toxicants interact in a mixture

Answer 2

• additive
• synergistic
• antagonistic

Question 3

additive

Answer 3

• the total amount of toxicity is the sum of the toxicants of the compounds (2+2=4)
• toxins are very similar (same LD50 or targets of toxicity)

Question 4

synergistic

Answer 4

total amount of toxicity is greater than the sum of the toxicities (2+2=8)

Question 5

antagonistic

Answer 5

total amount of toxicity is less than the sum of the toxicities of the compound (2+2=1)

Question 6

agonist vs antagonist

Answer 6

• activates the receptor

- deactivates the receptor

Question 7

interactions can occur between toxicants and abiotic factors

Answer 7

react to compounds in different ways in fresh water vs salt water

Question 8

potentiation

Answer 8

when a non-toxic chemical makes a different toxicant even more toxic

Question 9

toxicants exist in different chemical forms

Answer 9

forms can be either modified by metabolism by the individual or by environment-driven chemical reactions

Question 10

Karen Wetterhahn

Answer 10

expert in metal toxicity

Question 11

genotype

Answer 11

the genetic make up of an individual

Question 12

phenotype

Answer 12

observable traits due to interactions between the genotype and the environment

Question 13

genetics of the organism

Answer 13

-organisms from the same species share the same compliment of genes that collectively encode all the proteins

Question 14

mutation

Answer 14

• exchanging one nucleotide with another
• resistance evolves
• explain some variation in responses across a species

Question 15

polymorphisms

Answer 15

differences in the DNA sequences between individuals

Question 16

single nucleotide polymorphisms (SNPs)

Answer 16

• tell the difference between different genotypes in individuals
• can lead to differences in the amino acid sequence of the encoded proteins, changing how the protein functions

Question 17

susceptibility factors

Answer 17

protein that changed in a target of a toxicant, then the difference in function can affect the severity of the relative toxic effect

Question 18

resistance factors

Answer 18

genes encode enzymes that break down toxicants

Question 19

genome duplication events

Answer 19

• facilitate the evolution of resistance or tolerance to a toxicant
• random genome duplication can change the policy level of a species
• because there is an original copy that still functions in its normal way

Question 20

isoforms

Answer 20

• novel function can evolve in the extra copies of the genes

- tend to function in a tissue specific way

Question 21

age and size

Answer 21

• toxicant can have a greater effect at one of these stages

- smaller=easier to receive a toxic dose

Question 22

excretion/elimination rate

Answer 22

how long it takes to remove a compound from the tissue (excretion) or body of an organism (elimination)

Question 23

half-life

Answer 23

time it takes for a concentration to be reduced by half

Question 24

chronic or repeated doses can eventually reach toxic levels, depending on…

Answer 24

• the dose at each step of repeated exposure

- how quickly the toxicant is metabolized or excreted

Question 25

tolerance

Answer 25

-prior exposure to a toxicant alters the metabolism or physiology of the organism so that subsequent exposures to the same toxicant result in a reduced effect

Question 26

cross-tolerance

Answer 26

an individual becomes tolerant to different similar toxicants because of exposure to one compound

Question 27

resistance of a population or a species

Answer 27

• a genetic basis for the ability of an organism to avoid a toxic response when exposed to a toxicant
• mutations and evolution

Question 28

resistance mechanisms include

Answer 28

• selection for a resistance factor gene already in a population
• selection for a new mutation in a resistance factor gene
• multiple copies of a gene already in the organism arise
• a brand new gene picked up from the environment or another organism
• genetically engineered into a species

Question 29

selective sweep

Answer 29

• a new beneficial mutation rises in frequency in a population
• insecticide resistance or vaccines

Question 30

Insect resistance

Answer 30

-become resistant to compounds due to the huge selection pressure of using insecticides