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Ecotoxicology > Lecture 3 - DA > Flashcards

Lecture 3 - DA Flashcards

1
Q

How are toxicants classified?

A

Based on their chemical characteristics.

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2
Q

Is it useful to measure chemicals in the environment if theyre not bioavailable? Why/why not?

A

There is no use as it has no effect on the flora/fauna.

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3
Q

What are non essential metals?

A

Metals with no known function. Further research may reveal hidden purpose.

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4
Q

What kind of ion does a metal usually become, and which electrode will it go towards?

A

Forms cations that will go to the cathode.

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5
Q

Are metal ions positive and negative? Why?

A

They lose electrons, so they are positive.

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6
Q

What defines a heavy metal?

A

When atomic weight is over 40, and density relative to water is over 5.

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7
Q

Name 4 common heavy metals.

A

Copper, zinc, mercury, and lead.

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8
Q

Can heavy metals and alkali/alkali earth metals be trace metals?

A

Yes.

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9
Q

What are trace metals required for?

A

Metabolism.

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10
Q

What are metalloids? Name 4 examples.

A

Non-metallic elements such as silicon, arsenic, selenium, and boron.

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11
Q

Metals can be classified by density. What is an alternative?

A

Lewis acid properties.

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12
Q

What is a class A metal? What about class B? Can a metal be both?

A

A-oxygen seeking
B-sulphur/nitrogen seeking
Some metals may be borderline between the two.

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13
Q

Between class A and B metals, which one is essential for life? Which is more toxic?

A

Class A.

Class B is generally highly toxic.

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14
Q

True or false

Non-essential metals always have a tolerable level.

A

True.

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15
Q

Name 3 normal functions of metal ions.

A

Enzyme cofactors
Structural components - ie oxygen carriers
Ultratrace essentiality - encourages enzyme function

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16
Q

Define bioavailability of metals.

A

Fraction of metal an organism actually absorbs or accumulates.

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17
Q

Name 5 factors influencing bioavailability of metals.

A 
Total concentration
pH
Redox potential
Complexation
Organic content
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18
Q

Does low pH increase or decrease metal bioavailability?

A

Increase.

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19
Q

Does high temperature increase or decrease metal bioavailability?

A

Increase.

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20
Q

Does high salinity increase or decrease metal bioavailability?

A

Decrease.

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21
Q

Between organic and inorganic mercury, which is more bioavailable?

A

Organic.

Inorganic isnt very bioavailable.

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22
Q

Which ionic state of metals is most biologically active?

A

Divalent and trivalet

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23
Q

What is the toxicity of a metal determined by?

A

Rate of uptake, and rate of degradation to release the metal ion.

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24
Q

Why are organic molecules typically more toxic than inorganic molecules?

A

Due to increased lipophilicity.

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25
Q

What does the strength of a metal cation with an organic molecule reveal?

A

It is an expression of the toxicity.

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26
Q

Name 3 toxic effects metals can have.

A

Blocking essential function of biomolecules by interfering
Displacing essential metal ions in cofactors
Alter or modify the configuration of biomolecules

27
Q

Which enzyme production does lead interfere with? What does this result in?

A

ALAD

Results in impaired haemoglobin synthesis leading to anaemia.

28
Q

What does mercury interfere with?

A

Catecholamines, resulting in increased incidences of cardiovascular diseases.

29
Q

What does arsenic disrupt?

A

Normal aerobic respiration, leading to ROS formation.

30
Q

Give an example of cation displacement for the following:

  • reaction still occurs
  • permanent inactivity
A

Reaction still occurs
Be2+ replacing Mg2+
Permanent inactivity
Co2+ replaces Zn2+

31
Q

How do organisms detoxify metals?

A

Done by complexing them with metallothioneins - MTs

32
Q

What amino acid is metallothionein rich in?

A

Cysteine.

33
Q

Where are MTs deposited after complexing with metals, and in what form? How are they removed entirely?

A

Deposited as insoluble granules in the hepatopancreas, liver, and kidney.
Later excreted via faeces.

34
Q

What can gas chromatography and mass spectrometry reveal about metal toxicants? Can the toxicant be identified? Can they be quantified?

A

they can seperate organic metal molecules, identify them, and quantify them.

35
Q

What can pulse polarigraphy reveal about metal toxicants?

A

Quantity and ionic state.

36
Q

What is the difference between a total metal analysis and individual type analysis? Do they both reveal bioavailability?

A

Total - easy, less expensive. Less meanifgul - doesnt reveal bioavailability.
Individual type - harder, more expensive, but reveals bioavailability.

37
Q

In what form is mercury most released into the environment?

A

As inorganic mercury.

38
Q

What is the most important form of mercury? Can this form cross the blood-brain barrier?

A

Methylmercury, extremely toxic. Can cross the blood-brain barrier.

39
Q

What are the biological effects of methylmercury? Can it be excreted?

A

Causes minamata disease. Cannot be excreted - cumulative poison.

40
Q

Where does methylmercury accumulate in birds? Can they excrete it?

A

Liver and feathers. Excreted when moulting.

41
Q

Which cadmium ionic state is more common, Cd2+ or Cd1+?

A

Cd2+ is more common.

42
Q

What are 3 uses of cadmium?

A

Batteries, pigments, and plastics.

43
Q

Can cadmium be excreted by mammals and fish? Does it accumulate?

A

Doesnt accumulate in mammals or fish, is excreted.

Molluscs accumulate it.

44
Q

What disease and biological effects does excess cadmium cause?

A

Itai itai disease.

Severe bone deformities.

45
Q

What is the major problematic ionic state of lead? Does it cross the blood-brain barrier?

A

Pb2+

Small percentage crosses the blood-brain barrier.

46
Q

What values of pH and water hardness favours Pb2+?

A

Low pH and low water hardness.

47
Q

Where does Pb2+ accumulate?

A

Trout and mussels.

48
Q

What effect does lead have on children?

A

Affects mental development, even in adults, but especially in children.

49
Q

What are 3 sublethal symptoms of lead poisoning?

A

Kidney dysfunction
Anaemia
Neurological defects

50
Q

What ionic state of cooper is most common? Which other 3 are less common?

A

1, 3, and 4 are less common.

51
Q

Is copper essential for biological systems?

A

Yes.

52
Q

What metal is zinc like? Is it essential? Name 2 functions.

A

Like copper, is essential.

Needed for respiration and alcohol detoxification.

53
Q

What form of tin is extremely toxic? What effect does it have on plankton, oysters, and female marine snails?

A

Tributyl tin - TBT
Lethal to plankton.
Distorts oyster shells
Female marine snails grow penis and sperm duct

54
Q

What is imposex?

A

Imposition of the opposite sexual characteristics.

55
Q

What ionic state of aluminium is most common? Which other two are also found?

A

Al3+ most common

Also 1+ and 2+.

56
Q

Does low pH increase or decrease solubility of Al in water? What effect does this have on bioavailability?

A

Low pH increases solubility, increasing bioavailability.

57
Q

What neurological condition has aluminium been implicated in?

A

Alzheimers disease, not enough evidence.

58
Q

What effect does auminium have on plants?

A

Damaged roots

Reduced growth in acid due to increased Al3+ bioavailability.

59
Q

What form of arsenic is most toxic?

A

Arsenic gas.

60
Q

What is a sublethal effect of arsenic on fish? Is it toxic to algae?

A

Causes reproductive effects.

Toxic to sensitive algae.

61
Q

What does arsenic do to erythrocytes?

A

Breaks them down.

62
Q

Define metal biomethylation. Where can it occur?

A

Conversion of the inorganic form to the organic form.

Can occur in bacteria - bacterial methylation.

63
Q

What happens after metal biomethylation?

A

Enhanced toxicity and bioconcentration.

64
Q

After metal biomethylation, can demethylation occur?

A

Yes, it is then taken up by fish, eaten by humans.

Ecotoxicology (22 decks)

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