Bioaccumulation and Toxicokinetics

Question 1

What is net bioaccumulation?

Answer 1

uptake - elimination

Question 2

Why does bioaccumulation occur?

Answer 2

The elimination process is slower than the uptake

Question 3

What are the two phases of bioaccumulation?

Answer 3

accumulation and depurination

Question 4

What is the depurination phase?

Answer 4

excretion of chemical is greater than accumulation

Question 5

Why is the rate of excretion so dependent on the chemical itself?

Answer 5

lipophilicity and ability to be biotransformed

Question 6

What is the phenomenon known as growth dilution?

Answer 6

[toxicant] can decrease in growing organism due to the fact that the tissue growth is greater than the rate of uptake

Question 7

What type of chemicals exhibit growth dilution and where in the world does it commonly occur?

Answer 7

seen with some elements and warmer climates because cold inhibits tissue growth

Question 8

What is bioconcentration?

Answer 8

uptake of a dissolved phase of a toxicant to achieve total body conc. that exceed those in water

Question 9

What is biomagnification?

Answer 9

levels of toxicant increases as trophic levels increase

Question 10

What are some examples of toxicants that undergo biomagnification?

Answer 10

highly lipophilic toxicants

Question 11

What are three factors that contribute to the bioavailability of a toxicant?

Answer 11

physical, chemical and biological

Question 12

What two factors are toxicity defining?

Answer 12

chemical and physical factors of environment and toxicant

Question 13

What two factors influence absorption the most?

Answer 13

lipophilicity and concentration gradient

Question 14

What are the channels used for facilitated diffusion and what toxicants do they transport?

Answer 14

Ion gated-Ca2+ analogs like lead and Na+ analogs like Ag+ and Cu+
Ion non gated-Ca2+ analogs
OATS-for oxyanions like AsO3-

Question 15

What is the pump used for active transport and what does it transport?

Answer 15

Na/K pump can pump Cu and Ag against gradient

Question 16

What type of toxicants transported by endocytosis?

Answer 16

often large particles, ex ultrafine particles in lungs

Question 17

What is paracellular transport?

Answer 17

When very small toxicants can enter cell through gap junctions

Question 18

What are the factors affecting distribution?

Answer 18

lipophilicity and carrier proteins

Question 19

What are examples of carrier proteins?

Answer 19

albumin-binds all sorts of toxicants
ferritin-used in body for iron but can bind cadmium

Question 20

What is biotransformation?

Answer 20

Chemically changing the toxicant so it can be excreted in the body

Question 21

Why is the process of biotransformation so highly conserved if toxicants were never seen in the early days of life?

Answer 21

These processes were/are used to excrete steroid hormones

Question 22

Why do some toxicants not need a second biotransformation phase?

Answer 22

hydrophilic molecules are easier to excrete and do not need extra hydrophilic groups

Question 23

What are the main ways of excretion?

Answer 23

urine, feces, bile and respiration

Question 24

What are some examples of major organic pollutants?

Answer 24

Polycyclic aromatic hydrocarbons-napthalene
Polychlorinated biphenyls
Chlorinated phenols, dioxins and dibenzofurans (POPs)
Pesticides
Aromatic herbicides

Question 25

What are examples of inorganic pollutants?

Answer 25

metals and metalloids nonmetal inorganics-Cl and ammonia Inorganic gases-CO2

Question 26

What are the other three classes of pollutants?

Answer 26

Radionuclides-uranium Nutrients-PO4, NO3 Organometallics- methyl mercury, tributyl tin

Question 27

What is bioavailability?

Answer 27

the extent at which a contaminant is available for uptake

Question 28

What are some of the ways organic pollutants are made less bioavailable in the environment?

Answer 28

degradation from microbes or sunlight, and sequesteration

Question 29

What is the range for LogKow and what occurs at high lipophilicity?

Answer 29

-3 -7, will precipitate and leads to greater bioaccumulation

Question 30

What is LogKoa?

Answer 30

a measure of volatility and lipophilicity

Question 31

What is the relationship between volatility and lipophilicity?

Answer 31

As lipophilicity increases, volatility decreases

Question 32

What are the two abiotic factors affecting toxicity?

Answer 32

Natural organic matter and temperature

Question 33

How does temperature affect toxicity?

Answer 33

as temperature increases, membrane fluidity increases and therefore toxicity increases

Question 34

How does natural organic matter affect toxicity?

Answer 34

Highly lipophilic poles that can absorb contaminants and therefore cannot be taken up by organisms

Question 35

What are the biotic factors affecting toxicity?

Answer 35

age, sex, genetics and disease