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Ecotoxicology > Ch 2c > Flashcards

Ch 2c Flashcards

1
Q

Who was responsible for the recognition that all substances are poisonous given a sufficient concentration

A

Parcelsus (1493-1541)

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2
Q

True or false: everything is poisonous at a high enough dose

A

True

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3
Q

What are the three ideas that summarize toxicology on a biochemical scale

A
  1. toxic molecules react with biomolecules and disturb their normal processes
  2. as toxic concentration increases, so does the severity of the symptoms at the site of action
  3. concentration of the toxin at the action site increases with increasing does
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4
Q

What happens when toxic molecules react with biomolecules

A

they disturb their normal processes

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5
Q

What occurs as the concentration of a toxin increases

A

severity of the symptoms at the cite of action

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6
Q

What happens when you increase the concentration of a toxin at the site of action

A

the dose increases

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7
Q

True or False: a toxin can only have one mode of action

A

False

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8
Q

True or False: toxins that use the same category of the toxicity mechanism must be chemically related

A

FALSE

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9
Q

What are the general ways that toxins can cause death

A
  • Enzymes inhibitors
  • Disturbance of chemical signal systems
  • Toxins that generate free radical that destroy cellular components
  • Weak acids/bases that dissipate the pH gradients across membranes
  • Toxins that dissolve in the membrane and disturb their physical structure
  • Toxins that disturb the electrolyte or osmotic balance or the pH
  • Strong electrophiles, bases, acids, oxidants, or reductants that destroy tissue, DNA or proteins
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10
Q

What is an Enzyme inhibitor

A

Toxic substances may interact with an enzyme or transport protein to inhibit its normal function.

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11
Q

Where do enzyme inhibitors interact

A

at the active site or an allosteric site

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12
Q

What is an allosteric site

A

a site that will change the activity of an enzyme without changing the shape of the active site

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13
Q

True or False: Adding more substrate can overcome enzyme inhibition bound at the allosteric site

A

False

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14
Q

True of False: many enzymes have a SH group in the active site

A

True

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15
Q

Why do heavy metals work as enzyme inhibitors

A

Because substances like Hg2+ have a strong affinity for SH groups and will inactivate such enzymes

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16
Q

What does the potency of an enzyme inhibitor depend on

A

The enzyme and its relative importance in the cell

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17
Q

True of False: plants have a nervous system

A

False

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18
Q

why do organophosphate insecticides work on insects but not plants

A

because plants dont have a nervous system and dont often use the enzyme acetyl cholinesterase since insects do use this enzyme (to control muscles) you can harm the insects and not the plant

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19
Q

How does Glyphosate (round up) work

A

it inhibits the formation of aromatic amino acids (tryptophan, tyrosine and phenylalanine) in plants

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20
Q

What enzyme does glyphosate target

A

EPSPS (theres a long name too)

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21
Q

What does glyphosate work on plants and microorganisms but not animals

A

because then enzyme they target is not in animals

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22
Q

What is a systemic herbicide

A

it is transported throughout the plant before it is metabolized.

23
Q

True or False: Glyphosate is a systemic herbicide

A

True

24
Q

What pathway does EPSPS use to make for aromatic amino acid biosynthesis

A

The Shikimate Pathway

25
Q

How does the the shikimate pathway use EPSPS

A

Look at notes ch.2c page 4. Its too long to type out

26
Q

True or False: Chemical signals are used at all levels of organization

A

True

27
Q

How can toxins disrupt processes

A

By acting as an agonist or antagonists

28
Q

What is an agonist in terms of disturbing chemical signals

A

imitate the true signals

-This results in signals that are too strong, last too long or are incorrectly times

29
Q

Explain how nicotine works as an agonists

A

it acts similarly to acetylcholine in the nervous system, but isnt inactivated by acetylcholinesterase

30
Q

How does 2,4-D (thing in agent orange) act as a agonists

A

mimics the plant hormone auxin and causes uncontrolled growth leading to disruption of water and nutrient movement

31
Q

What is an Antagonist

A

Something that blocks the binding site for the true signal

32
Q

What is an examples of antagonism

A
  • curare
  • for the acetylcholine receptors on the muscle side of the neuromuscular junction
  • prevents muscular contraction in response to the nerve signal
  • causes flaccid paralysis
  • death by asphyxia
  • fully aware until loss of consciousness due to lack of o2
33
Q

How do toxins generate free radicals that destroy cellular components

A

components can be oxidized or reduced by single electron transfers rather then the more usual two electron transfers
-Often involve production of superoxide anion (02-) as a precursor to the production of OH

34
Q

What does hydroxyl do to molecules

A
  • it non-specifically attacks the first molecule it meets to steel and electron
  • results in cascade where a new radical is made
  • can cause extensive cellular damage to proteins, DNA RNA ect.
35
Q

What are some examples of toxins that can catalyze a free radical cascade reaction

A

Fe, Cu, Mg, Cobalt

36
Q

How can paraquat produce a superoxide anion

A

by taking an electron from the ETC and giving it to O2

37
Q

How do cells protect themselves against radicals

A

-Enzymes to defend against (superoxide dismutase, catalase, ect)

38
Q

True or False: Cells have repair enzymes for some damage caused by free radicals

A

True

39
Q

What is the proton motive force

A

A pH gradient that s used to harness energy (make ATP) move cells and in the transport process.
-occurs across the inner mitochondrial membrane (thylakiod membrane in plant chloroplasts or the plasma membrane in bacteria)

40
Q

How do some toxins move their protons down the concentration gradient in a cell

A

-by dissolving in cell membrane

41
Q

What happens when a toxin dissolved in cell membrane

A

-Dissipates the pH gradient and brings process dependant on the PMF (proton motive force) to a halt

42
Q

What are uncoupling agents

A

toxins that dissipate the pH gradients across membranes

43
Q

what are examples of uncoupling agents

A

ammonia, phenol, acetic acid

44
Q

how do organisms deal with uncoupling agents

A

-by binding them into glutamine/urea; -movement into Krebs cycle

45
Q

What are examples of toxins that dissolve in the membrane and disturb their physical structure

A
  • Alcohols
  • gasoline
  • PAH
  • Chlorinated hydrocarbons
46
Q

what do toxins that dissolve the membrane disrupt

A

interactions between adjacent phospholipids and can make the membrane leaky

47
Q

What is an example of a toxin that disturbs the electrolyte or osmotic balance or pH

A

-Sodium chloride and other salts are essential to life but in high doses disrupt the osmotic balance across membranes

48
Q

True or False: Salinity can be a limiting factor for life

A

True

49
Q

True or False: pH can be a limiting factor for life

A

True

50
Q

Can pH change the relative solubility of other ions

A

Yes

51
Q

Why do strong electrophiles, bases, acids, oxidants or reductants destroy tissue, DNA or proteins

A
  • Dissolve and destroy tissue

- Electrophilic substances can react with DNA and potentially cause cancer

52
Q

True or False: Strong electrophiles, bases, oxidants or reductants that destroy tissue, DNA or proteins are more important from an ecotoxicology perspective then a safety perspective

A

False: more important from a safety perspective (except for spills)

53
Q

True or False: electrophilic substances can be the original substance or a product produced by the liver

A

True

Ecotoxicology (13 decks)

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