Unit 1

Question 1

Define ecotoxicology

Answer 1

Science of contaminants in the biosphere and their effects of constituents of that biosphere including humans.

Question 2

Clearly describe the similarities and differences between the three goals of ecotoxicology (scientific, technical and practical).

Answer 2

Science: Organize knowledge based on explanatory principles about contaminants in the biosphere (scientific method)

Technological: develop and apply tools to acquire a better understanding of contaminant fate

Practical (Reg): apply the available knowledge tools to solve or document problems

Question 3

Describe the dilution paradigm and the boomerang paradigm.

Why and how we moved from dilution to boomerang?

Answer 3

The dilution paradigm - “the solution to pollution is dilution”
Boomerang paradigm - “What you throw away can come back and hurt you”

There were two heavy metal poisoning incidents which led to the replacement of the dilution paradigm to the boomerang paradigm

Question 4

Differentiate between a contaminant and a pollutant.

Answer 4

Contaminant: substance released by humans
Pollutant: substance occurs in the environment due to human activities and has a deleterious effect

Question 5

Explain what contaminant partitioning is and why it is important in ecotoxicology.

Answer 5

it is a transport process that is influenced by how contaminant partitions between phases
(gas/aqueous, aqueous/sediment and dissolved liquid/solid)

Determine its final destination

Question 6

Explain what a POP is?

Answer 6

Persistent Organic Pollutant, synthetic chemical with unique and dangerous characteristics

Question 7

Describe the major classes of contaminants and give an example of each class?

Answer 7

Organic compound: used as poisons, by-products, and products for industrial activities

Inorganic gases: CO2, NOx , SOx

Metals and Metalliods: Al, As, Cd, Cr and Cu

Nutrients: Nitrogen species, Phosphates species

Organometals: Tin, Pb, Hg and radionuclides

Question 8

Clearly distinguish between bioaccumulation and bioconcentration?

Answer 8

Bioaccumulation is the net amount of a contaminant on or in an organism from all sources.

Bioconcentration is accumulation is or on an organism from water.

Question 9

Clearly delineate exposure routes for an organism

Answer 9

Lipid route: dissolve from the membrane.
Aqueous route anything that has a transport channel.
Endocytotic: active process example amoeba comes as membrane-bound vesicles.

Question 10

Clearly distinguish between steady state and equilibrium

Answer 10

steady state of a system is when the conditions do not change in time and requires energy

Equilibrium state of a system in which the properties become uniforms and doesnt require energy

Question 11

Distinguish between diffusion, facilitated diffusion and active transport

Answer 11

Diffusion: no energy, molecule moves across membrane down its concentration (gated or ungated, may have channel protein)

Facilitated diffusion: no energy, needs a carrier protein, moves with concentration gradient (faster than diffusion)

Active transport: Energy required (ATP or PMF)
carrier proteins involved, (Na+/K+ pump)

Question 12

Described the relationship between biotransformation and activation with examples

Answer 12

Biotransformation: conversion of one chemical compound to another (Fermentation, probiotics)
Activation: one possible consequence of biotransformation is when the effect of the active compound is worsened or inactive
(organophosphorus pesticide, parathion undergoes oxidation desulfuration to form the very potent paraoxon)

Question 13

Explain what metallothionein is and what is used for?

Answer 13

Class of smaller proteins with 30% of their amino acids being sulfur rich cysteine and possess the capacity to bind six to seven metal atoms per molecule

(Cd, Cu, Hg, Zn, Ag and Pb)
induced when metal concentrations are higher and help with metal homeostasis

Question 14

Describe the roles of Phase I and Phase II reactions

Answer 14

Phase I: increasing reactivity and hydrophilicity
- involves the addition of oxygen to xenobiotic by a monooxygenase

Phase II: conjugated are formed by phase II reactions which inactivate and cause elimination of the compound
- compounds conjugate with xenobiotics or their biotransformation products include acetate, cysteine, sulfate, glycine and glutamine

Question 15

Explain how enterohepatic can increase the damage a toxin may do

Answer 15

Enterohepatic Circulation - there is recirculation of a toxicant back to the liver after passing through the intestine in bile and then reabsorbed in the intestine

• may increase the persistence of some compounds

Question 16

How can the bioavailability from two different exposure routes can be determined

Answer 16

Bioavailability: the extent to which a contaminant in a source is free for uptake.
By looking at the route targe,
dermal looking at skin, inhalation looking at lungs

Question 17

Chemical qualities that can alter bioavailability of a toxicant
from water for organic and for metals

Answer 17

pH, temperature, Ionic strength, speciation of metals

Question 18

Chemical qualities that can alter bioavailability of a toxicant
from solid for organic and for metals

Answer 18

Particle size

Question 19

Define allometry and describe its influence on bioavailability

Answer 19

It is the study of the effects of size, It may alter metabolic rate, anatomy and physiology

Question 20

What is the difference between a biologically determinant and indeterminant element

Answer 20

Determinant: elements whose concentrations in the body remain relatively constant spite environmental conditions
(sodium, calcium and potassium)

Indeterminant: elements whose concentration in the organism are proportional to the environmental conditions

Question 21

Explain the types of situations that may be mistaken for biomagnification

Answer 21

Lipid concentrations may be higher in predators, metaolic differences, life span

Prey grow faster and have more growth dilution.

Question 22

Explain the twin tracer technique and how it can be used to measure assimilation from food

Answer 22

Feed both substances and follow the appearance of the inert tracer in feces or urine

Look for the assimilation of the substance of interest and compare