Ch 2c Flashcards
Who was responsible for the recognition that all substances are poisonous given a sufficient concentration
Parcelsus (1493-1541)
True or false: everything is poisonous at a high enough dose
True
What are the three ideas that summarize toxicology on a biochemical scale
- toxic molecules react with biomolecules and disturb their normal processes
- as toxic concentration increases, so does the severity of the symptoms at the site of action
- concentration of the toxin at the action site increases with increasing does
What happens when toxic molecules react with biomolecules
they disturb their normal processes
What occurs as the concentration of a toxin increases
severity of the symptoms at the cite of action
What happens when you increase the concentration of a toxin at the site of action
the dose increases
True or False: a toxin can only have one mode of action
False
True or False: toxins that use the same category of the toxicity mechanism must be chemically related
FALSE
What are the general ways that toxins can cause death
- 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
What is an Enzyme inhibitor
Toxic substances may interact with an enzyme or transport protein to inhibit its normal function.
Where do enzyme inhibitors interact
at the active site or an allosteric site
What is an allosteric site
a site that will change the activity of an enzyme without changing the shape of the active site
True or False: Adding more substrate can overcome enzyme inhibition bound at the allosteric site
False
True of False: many enzymes have a SH group in the active site
True
Why do heavy metals work as enzyme inhibitors
Because substances like Hg2+ have a strong affinity for SH groups and will inactivate such enzymes
What does the potency of an enzyme inhibitor depend on
The enzyme and its relative importance in the cell
True of False: plants have a nervous system
False
why do organophosphate insecticides work on insects but not plants
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
How does Glyphosate (round up) work
it inhibits the formation of aromatic amino acids (tryptophan, tyrosine and phenylalanine) in plants
What enzyme does glyphosate target
EPSPS (theres a long name too)
What does glyphosate work on plants and microorganisms but not animals
because then enzyme they target is not in animals
What is a systemic herbicide
it is transported throughout the plant before it is metabolized.
True or False: Glyphosate is a systemic herbicide
True
What pathway does EPSPS use to make for aromatic amino acid biosynthesis
The Shikimate Pathway
How does the the shikimate pathway use EPSPS
Look at notes ch.2c page 4. Its too long to type out
True or False: Chemical signals are used at all levels of organization
True
How can toxins disrupt processes
By acting as an agonist or antagonists
What is an agonist in terms of disturbing chemical signals
imitate the true signals
-This results in signals that are too strong, last too long or are incorrectly times
Explain how nicotine works as an agonists
it acts similarly to acetylcholine in the nervous system, but isnt inactivated by acetylcholinesterase
How does 2,4-D (thing in agent orange) act as a agonists
mimics the plant hormone auxin and causes uncontrolled growth leading to disruption of water and nutrient movement
What is an Antagonist
Something that blocks the binding site for the true signal
What is an examples of antagonism
- 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
How do toxins generate free radicals that destroy cellular components
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
What does hydroxyl do to molecules
- 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.
What are some examples of toxins that can catalyze a free radical cascade reaction
Fe, Cu, Mg, Cobalt
How can paraquat produce a superoxide anion
by taking an electron from the ETC and giving it to O2
How do cells protect themselves against radicals
-Enzymes to defend against (superoxide dismutase, catalase, ect)
True or False: Cells have repair enzymes for some damage caused by free radicals
True
What is the proton motive force
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)
How do some toxins move their protons down the concentration gradient in a cell
-by dissolving in cell membrane
What happens when a toxin dissolved in cell membrane
-Dissipates the pH gradient and brings process dependant on the PMF (proton motive force) to a halt
What are uncoupling agents
toxins that dissipate the pH gradients across membranes
what are examples of uncoupling agents
ammonia, phenol, acetic acid
how do organisms deal with uncoupling agents
-by binding them into glutamine/urea; -movement into Krebs cycle
What are examples of toxins that dissolve in the membrane and disturb their physical structure
- Alcohols
- gasoline
- PAH
- Chlorinated hydrocarbons
what do toxins that dissolve the membrane disrupt
interactions between adjacent phospholipids and can make the membrane leaky
What is an example of a toxin that disturbs the electrolyte or osmotic balance or pH
-Sodium chloride and other salts are essential to life but in high doses disrupt the osmotic balance across membranes
True or False: Salinity can be a limiting factor for life
True
True or False: pH can be a limiting factor for life
True
Can pH change the relative solubility of other ions
Yes
Why do strong electrophiles, bases, acids, oxidants or reductants destroy tissue, DNA or proteins
- Dissolve and destroy tissue
- Electrophilic substances can react with DNA and potentially cause cancer
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
False: more important from a safety perspective (except for spills)
True or False: electrophilic substances can be the original substance or a product produced by the liver
True
