Lecture 3 - DA

Question 1

How are toxicants classified?

Answer 1

Based on their chemical characteristics.

Question 2

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

Answer 2

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

Question 3

What are non essential metals?

Answer 3

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

Question 4

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

Answer 4

Forms cations that will go to the cathode.

Question 5

Are metal ions positive and negative? Why?

Answer 5

They lose electrons, so they are positive.

Question 6

What defines a heavy metal?

Answer 6

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

Question 7

Name 4 common heavy metals.

Answer 7

Copper, zinc, mercury, and lead.

Question 8

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

Answer 8

Yes.

Question 9

What are trace metals required for?

Answer 9

Metabolism.

Question 10

What are metalloids? Name 4 examples.

Answer 10

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

Question 11

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

Answer 11

Lewis acid properties.

Question 12

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

Answer 12

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

Question 13

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

Answer 13

Class A.

Class B is generally highly toxic.

Question 14

True or false

Non-essential metals always have a tolerable level.

Answer 14

True.

Question 15

Name 3 normal functions of metal ions.

Answer 15

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

Question 16

Define bioavailability of metals.

Answer 16

Fraction of metal an organism actually absorbs or accumulates.

Question 17

Name 5 factors influencing bioavailability of metals.

Answer 17

Total concentration
pH
Redox potential
Complexation
Organic content

Question 18

Does low pH increase or decrease metal bioavailability?

Answer 18

Increase.

Question 19

Does high temperature increase or decrease metal bioavailability?

Answer 19

Increase.

Question 20

Does high salinity increase or decrease metal bioavailability?

Answer 20

Decrease.

Question 21

Between organic and inorganic mercury, which is more bioavailable?

Answer 21

Organic.

Inorganic isnt very bioavailable.

Question 22

Which ionic state of metals is most biologically active?

Answer 22

Divalent and trivalet

Question 23

What is the toxicity of a metal determined by?

Answer 23

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

Question 24

Why are organic molecules typically more toxic than inorganic molecules?

Answer 24

Due to increased lipophilicity.

Question 25

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

Answer 25

It is an expression of the toxicity.

Question 26

Name 3 toxic effects metals can have.

Answer 26

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

Question 27

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

Answer 27

ALAD | Results in impaired haemoglobin synthesis leading to anaemia.

Question 28

What does mercury interfere with?

Answer 28

Catecholamines, resulting in increased incidences of cardiovascular diseases.

Question 29

What does arsenic disrupt?

Answer 29

Normal aerobic respiration, leading to ROS formation.

Question 30

Give an example of cation displacement for the following: - reaction still occurs - permanent inactivity

Answer 30

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

Question 31

How do organisms detoxify metals?

Answer 31

Done by complexing them with metallothioneins - MTs

Question 32

What amino acid is metallothionein rich in?

Answer 32

Cysteine.

Question 33

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

Answer 33

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

Question 34

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

Answer 34

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

Question 35

What can pulse polarigraphy reveal about metal toxicants?

Answer 35

Quantity and ionic state.

Question 36

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

Answer 36

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

Question 37

In what form is mercury most released into the environment?

Answer 37

As inorganic mercury.

Question 38

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

Answer 38

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

Question 39

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

Answer 39

Causes minamata disease. Cannot be excreted - cumulative poison.

Question 40

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

Answer 40

Liver and feathers. Excreted when moulting.

Question 41

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

Answer 41

Cd2+ is more common.

Question 42

What are 3 uses of cadmium?

Answer 42

Batteries, pigments, and plastics.

Question 43

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

Answer 43

Doesnt accumulate in mammals or fish, is excreted. | Molluscs accumulate it.

Question 44

What disease and biological effects does excess cadmium cause?

Answer 44

Itai itai disease. | Severe bone deformities.

Question 45

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

Answer 45

Pb2+ | Small percentage crosses the blood-brain barrier.

Question 46

What values of pH and water hardness favours Pb2+?

Answer 46

Low pH and low water hardness.

Question 47

Where does Pb2+ accumulate?

Answer 47

Trout and mussels.

Question 48

What effect does lead have on children?

Answer 48

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

Question 49

What are 3 sublethal symptoms of lead poisoning?

Answer 49

Kidney dysfunction Anaemia Neurological defects

Question 50

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

Answer 50

1, 3, and 4 are less common.

Question 51

Is copper essential for biological systems?

Answer 51

Yes.

Question 52

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

Answer 52

Like copper, is essential. | Needed for respiration and alcohol detoxification.

Question 53

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

Answer 53

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

Question 54

What is imposex?

Answer 54

Imposition of the opposite sexual characteristics.

Question 55

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

Answer 55

Al3+ most common | Also 1+ and 2+.

Question 56

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

Answer 56

Low pH increases solubility, increasing bioavailability.

Question 57

What neurological condition has aluminium been implicated in?

Answer 57

Alzheimers disease, not enough evidence.

Question 58

What effect does auminium have on plants?

Answer 58

Damaged roots | Reduced growth in acid due to increased Al3+ bioavailability.

Question 59

What form of arsenic is most toxic?

Answer 59

Arsenic gas.

Question 60

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

Answer 60

Causes reproductive effects. | Toxic to sensitive algae.

Question 61

What does arsenic do to erythrocytes?

Answer 61

Breaks them down.

Question 62

Define metal biomethylation. Where can it occur?

Answer 62

Conversion of the inorganic form to the organic form. | Can occur in bacteria - bacterial methylation.

Question 63

What happens after metal biomethylation?

Answer 63

Enhanced toxicity and bioconcentration.

Question 64

After metal biomethylation, can demethylation occur?

Answer 64

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