Ch 2c

Question 1

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

Answer 1

Parcelsus (1493-1541)

Question 2

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

Answer 2

True

Question 3

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

Answer 3

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

Question 4

What happens when toxic molecules react with biomolecules

Answer 4

they disturb their normal processes

Question 5

What occurs as the concentration of a toxin increases

Answer 5

severity of the symptoms at the cite of action

Question 6

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

Answer 6

the dose increases

Question 7

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

Answer 7

False

Question 8

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

Answer 8

FALSE

Question 9

What are the general ways that toxins can cause death

Answer 9

• 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

Question 10

What is an Enzyme inhibitor

Answer 10

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

Question 11

Where do enzyme inhibitors interact

Answer 11

at the active site or an allosteric site

Question 12

What is an allosteric site

Answer 12

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

Question 13

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

Answer 13

False

Question 14

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

Answer 14

True

Question 15

Why do heavy metals work as enzyme inhibitors

Answer 15

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

Question 16

What does the potency of an enzyme inhibitor depend on

Answer 16

The enzyme and its relative importance in the cell

Question 17

True of False: plants have a nervous system

Answer 17

False

Question 18

why do organophosphate insecticides work on insects but not plants

Answer 18

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

Question 19

How does Glyphosate (round up) work

Answer 19

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

Question 20

What enzyme does glyphosate target

Answer 20

EPSPS (theres a long name too)

Question 21

What does glyphosate work on plants and microorganisms but not animals

Answer 21

because then enzyme they target is not in animals

Question 22

What is a systemic herbicide

Answer 22

it is transported throughout the plant before it is metabolized.

Question 23

True or False: Glyphosate is a systemic herbicide

Answer 23

True

Question 24

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

Answer 24

The Shikimate Pathway

Question 25

How does the the shikimate pathway use EPSPS

Answer 25

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

Question 26

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

Answer 26

True

Question 27

How can toxins disrupt processes

Answer 27

By acting as an agonist or antagonists

Question 28

What is an agonist in terms of disturbing chemical signals

Answer 28

imitate the true signals | -This results in signals that are too strong, last too long or are incorrectly times

Question 29

Explain how nicotine works as an agonists

Answer 29

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

Question 30

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

Answer 30

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

Question 31

What is an Antagonist

Answer 31

Something that blocks the binding site for the true signal

Question 32

What is an examples of antagonism

Answer 32

- 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

Question 33

How do toxins generate free radicals that destroy cellular components

Answer 33

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*

Question 34

What does hydroxyl do to molecules

Answer 34

- 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.

Question 35

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

Answer 35

Fe, Cu, Mg, Cobalt

Question 36

How can paraquat produce a superoxide anion

Answer 36

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

Question 37

How do cells protect themselves against radicals

Answer 37

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

Question 38

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

Answer 38

True

Question 39

What is the proton motive force

Answer 39

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)

Question 40

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

Answer 40

-by dissolving in cell membrane

Question 41

What happens when a toxin dissolved in cell membrane

Answer 41

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

Question 42

What are uncoupling agents

Answer 42

toxins that dissipate the pH gradients across membranes

Question 43

what are examples of uncoupling agents

Answer 43

ammonia, phenol, acetic acid

Question 44

how do organisms deal with uncoupling agents

Answer 44

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

Question 45

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

Answer 45

- Alcohols - gasoline - PAH - Chlorinated hydrocarbons

Question 46

what do toxins that dissolve the membrane disrupt

Answer 46

interactions between adjacent phospholipids and can make the membrane leaky

Question 47

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

Answer 47

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

Question 48

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

Answer 48

True

Question 49

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

Answer 49

True

Question 50

Can pH change the relative solubility of other ions

Answer 50

Yes

Question 51

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

Answer 51

- Dissolve and destroy tissue | - Electrophilic substances can react with DNA and potentially cause cancer

Question 52

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

Answer 52

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

Question 53

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

Answer 53

True