Lecture 3 - DA Flashcards
How are toxicants classified?
Based on their chemical characteristics.
Is it useful to measure chemicals in the environment if theyre not bioavailable? Why/why not?
There is no use as it has no effect on the flora/fauna.
What are non essential metals?
Metals with no known function. Further research may reveal hidden purpose.
What kind of ion does a metal usually become, and which electrode will it go towards?
Forms cations that will go to the cathode.
Are metal ions positive and negative? Why?
They lose electrons, so they are positive.
What defines a heavy metal?
When atomic weight is over 40, and density relative to water is over 5.
Name 4 common heavy metals.
Copper, zinc, mercury, and lead.
Can heavy metals and alkali/alkali earth metals be trace metals?
Yes.
What are trace metals required for?
Metabolism.
What are metalloids? Name 4 examples.
Non-metallic elements such as silicon, arsenic, selenium, and boron.
Metals can be classified by density. What is an alternative?
Lewis acid properties.
What is a class A metal? What about class B? Can a metal be both?
A-oxygen seeking
B-sulphur/nitrogen seeking
Some metals may be borderline between the two.
Between class A and B metals, which one is essential for life? Which is more toxic?
Class A.
Class B is generally highly toxic.
True or false
Non-essential metals always have a tolerable level.
True.
Name 3 normal functions of metal ions.
Enzyme cofactors
Structural components - ie oxygen carriers
Ultratrace essentiality - encourages enzyme function
Define bioavailability of metals.
Fraction of metal an organism actually absorbs or accumulates.
Name 5 factors influencing bioavailability of metals.
Total concentration pH Redox potential Complexation Organic content
Does low pH increase or decrease metal bioavailability?
Increase.
Does high temperature increase or decrease metal bioavailability?
Increase.
Does high salinity increase or decrease metal bioavailability?
Decrease.
Between organic and inorganic mercury, which is more bioavailable?
Organic.
Inorganic isnt very bioavailable.
Which ionic state of metals is most biologically active?
Divalent and trivalet
What is the toxicity of a metal determined by?
Rate of uptake, and rate of degradation to release the metal ion.
Why are organic molecules typically more toxic than inorganic molecules?
Due to increased lipophilicity.
What does the strength of a metal cation with an organic molecule reveal?
It is an expression of the toxicity.
Name 3 toxic effects metals can have.
Blocking essential function of biomolecules by interfering
Displacing essential metal ions in cofactors
Alter or modify the configuration of biomolecules
Which enzyme production does lead interfere with? What does this result in?
ALAD
Results in impaired haemoglobin synthesis leading to anaemia.
What does mercury interfere with?
Catecholamines, resulting in increased incidences of cardiovascular diseases.
What does arsenic disrupt?
Normal aerobic respiration, leading to ROS formation.
Give an example of cation displacement for the following:
- reaction still occurs
- permanent inactivity
Reaction still occurs
Be2+ replacing Mg2+
Permanent inactivity
Co2+ replaces Zn2+
How do organisms detoxify metals?
Done by complexing them with metallothioneins - MTs
What amino acid is metallothionein rich in?
Cysteine.
Where are MTs deposited after complexing with metals, and in what form? How are they removed entirely?
Deposited as insoluble granules in the hepatopancreas, liver, and kidney.
Later excreted via faeces.
What can gas chromatography and mass spectrometry reveal about metal toxicants? Can the toxicant be identified? Can they be quantified?
they can seperate organic metal molecules, identify them, and quantify them.
What can pulse polarigraphy reveal about metal toxicants?
Quantity and ionic state.
What is the difference between a total metal analysis and individual type analysis? Do they both reveal bioavailability?
Total - easy, less expensive. Less meanifgul - doesnt reveal bioavailability.
Individual type - harder, more expensive, but reveals bioavailability.
In what form is mercury most released into the environment?
As inorganic mercury.
What is the most important form of mercury? Can this form cross the blood-brain barrier?
Methylmercury, extremely toxic. Can cross the blood-brain barrier.
What are the biological effects of methylmercury? Can it be excreted?
Causes minamata disease. Cannot be excreted - cumulative poison.
Where does methylmercury accumulate in birds? Can they excrete it?
Liver and feathers. Excreted when moulting.
Which cadmium ionic state is more common, Cd2+ or Cd1+?
Cd2+ is more common.
What are 3 uses of cadmium?
Batteries, pigments, and plastics.
Can cadmium be excreted by mammals and fish? Does it accumulate?
Doesnt accumulate in mammals or fish, is excreted.
Molluscs accumulate it.
What disease and biological effects does excess cadmium cause?
Itai itai disease.
Severe bone deformities.
What is the major problematic ionic state of lead? Does it cross the blood-brain barrier?
Pb2+
Small percentage crosses the blood-brain barrier.
What values of pH and water hardness favours Pb2+?
Low pH and low water hardness.
Where does Pb2+ accumulate?
Trout and mussels.
What effect does lead have on children?
Affects mental development, even in adults, but especially in children.
What are 3 sublethal symptoms of lead poisoning?
Kidney dysfunction
Anaemia
Neurological defects
What ionic state of cooper is most common? Which other 3 are less common?
1, 3, and 4 are less common.
Is copper essential for biological systems?
Yes.
What metal is zinc like? Is it essential? Name 2 functions.
Like copper, is essential.
Needed for respiration and alcohol detoxification.
What form of tin is extremely toxic? What effect does it have on plankton, oysters, and female marine snails?
Tributyl tin - TBT
Lethal to plankton.
Distorts oyster shells
Female marine snails grow penis and sperm duct
What is imposex?
Imposition of the opposite sexual characteristics.
What ionic state of aluminium is most common? Which other two are also found?
Al3+ most common
Also 1+ and 2+.
Does low pH increase or decrease solubility of Al in water? What effect does this have on bioavailability?
Low pH increases solubility, increasing bioavailability.
What neurological condition has aluminium been implicated in?
Alzheimers disease, not enough evidence.
What effect does auminium have on plants?
Damaged roots
Reduced growth in acid due to increased Al3+ bioavailability.
What form of arsenic is most toxic?
Arsenic gas.
What is a sublethal effect of arsenic on fish? Is it toxic to algae?
Causes reproductive effects.
Toxic to sensitive algae.
What does arsenic do to erythrocytes?
Breaks them down.
Define metal biomethylation. Where can it occur?
Conversion of the inorganic form to the organic form.
Can occur in bacteria - bacterial methylation.
What happens after metal biomethylation?
Enhanced toxicity and bioconcentration.
After metal biomethylation, can demethylation occur?
Yes, it is then taken up by fish, eaten by humans.
