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BIOL354 Final Exam Flashcards
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- 1What are the degrees of response?Lethal: sufficient to cause death or a very rapid, catastrophic response
Sublethal: below a level that directly causes death - 2What are the types of responses?1. Population --> density, community, productivity, mating success, alterations in the genetic structure of the population
2. Whole organism --> mortality, reproduction, necrosis, tumours, growth and behavriour
3. Biochemical/metabolic --> enzyme inhibition, immunological suppression, endocrine induction, stress protein induction, DNA damage - 3Describe the timing of the responses.1. Acute --> a stimulus (contaminant) inducing a rapid response, typically from a brief/intense exposure of less than 4 days.
2. Chronic --> effect after prolonged exposure (usually more than 10% of the life span of the test organism); stimulus lingers or continues for a long period of time
3. Subacute --> stimulus that is less severe than an acute stimulus (slightly longer)
4. Cumulative --> toxicity brought about by successive additions at different times or in different ways. - 4What is the life cycle study?The study of lethality, growth, reproduction, and development over the entire life cycle of an organism.
- 5What is the difference between critical life stage testing and the early life stage test?Critical life stage testing looks at the toxicity at an important life stage (ex. neonate growth, or during reproduction). Early life stage testing is subset of the critical life stage test; looks at the most sensitive phase, which is in early development.
- 6What is the weakest link incongruity?When extrapolating from the critical life stage testing, there is a possibility of overestimation of risk since not all of the population will be at this stage.
- 7What are the 3 main components of a bioassay?1. Time - the time required for a given organism to respond to a given toxicant
2. Toxicant dose or concentration - the amount of toxicant required for the average organism to respond within a specified length of time
3. Test type - static toxicity, static renewal, flow through tests - 8What is the definition of a bioassay?An experiment for estimating the nature, constitution or potency of a contaminant, by testing the reaction of a biological organism.
- 9What is the individual effective dose?The smallest dose needed to kill or affect a particular individual at a particular time. A population is needed to create repeats of this test as the same individual will respond differently the second time.
- 10What does a dose/concentration response curve typically look like?A sigmoid shaped curve, plotting % responding (dead) vs concentration. Additional response gives a normal distribution.
- 11Define concentration and dose.Concentration - the amount of toxicant external to the organism on a volume basis.
Dose - the amount of toxicant applied internally to the organism - 12Define LC50 and EC50.LC50 - concentration that causes mortality in 50% of the organisms
EC50 - the concentration that causes an effect in 50% of the organisms, usually based on a non-lethal endpoint. - 13Define NOEC, NOEL, LOEC, AND LOEL.NOEC - no observed effects concentration
NOEL - no observed effects level, based on dose
LOEC - lowest observed effects concentration
LOEL - lowest observed effects level, based on dose - 14Define MTC and MATC.MTC - minimum threshold concentration, based on dose
MATC - maximum allowable toxicant concentration (set by officials). Requires data on survival, growth, and reproduction over the life cycle of the organism.
Typically, NOEC < MATC < LOEC - 15What is the benefit of using a probit scale?Probit scale - plot concentration on a log scale, response on a probit scale. This linearizes the curve and gives greatest confidence around EC50, although error increases as as you move away from it.
- 16How would you measure LT50?Time vs response graph
- Measure the number dead/affected as a function of time
- At one concentration, LT50 of different chemicals can be measured to compare toxicity. - 17What are some uses of lethal effects data?- Whole Effluent Testing can be used to decrease toxicity and hazards in industrial regions
- Database created for many chemicals
- Created the water quality criteria (WQC), used for the Clean Water Act - 18What is the difference between the Threshold Model and the Hormesis Model?Threshold Model: regular response curves
Hormesis Model: biphasic concentration response
- hormesis model is useful to measure low concentrations and chronic effects
- curve characterized by low-dose stimulation and high-dose inhibition - 19What should be considered when selecting a test organism?1. should be widely available
2. should be readily culturable in laboratories, in sufficient amounts
3. genetics and history of organism should be known
4. sensitivity of the species should be representative to the environment or a class of organisms
5. in multi-species tests, interactions between the tested organisms must be understood
6. must satisfy regulatory agency mandates - 20Describe the 48h acute test with Daphnia magna.- 10 neonates in a starvation test
- 100mL test solution, 5 concentrations + control in triplicate
- lighting: 16h light, 8h dark
- no static renewal needed
- death = endpoint; based on immobility
- measure at 24h intervals for 28h
- positive control: pentachlorophenol or copper - 21What are the advantages/disadvantages of the 48h acute test?Advantages: rapid, small amounts of hazardous waste, inexpensive, can be made into a chronic or life cycle test, can be used with bioindicator assessment
Disadvantages: daphnids have a higher average sensitivity to contaminants (also an adv.), sensitive to changes in water quality, starvation = extra stress, dose response curve often very steep - 22Describe the 8d growth assay of Lemna gibba.- 3 colonies from a log culture phase put into a synthetic growth medium
- 50mL test solution, 5 concentrations + control in triplicate
- light: 16h growth light/8h dark or continuous light
- static renewal needed
- endpoint = inhibition of growth
- measurements at 48h intervals over 8 days
- positive control: herbicides, ASA, NaCl, H3BO3 - 23What are the advantages/disadvantages of the 8d growth assay?Advantages: rapid, small amounts of hazardous waste, can be used with bioindicator assessment
Disadvantages: often has a lower than average sensitivity to contaminants, sensitive to light quality, media can complex metals, labour intensive - 24Describe the 1-4 week assay with Hyalella azteca.- uses 7-14 day old organisms
- 4 week reproduction assay
- 250mL test solution + substrate (cotton ball or sediment), 5 concentrations + control in triplicate
- static renewal required (food)
- lighting: 16h light/8h dark
- measurements taken at the end of the test
- positive control: copper or cadmium - 25What are the advantages/disadvantages of the assay?Advantages: small amounts of hazardous waste, inexpensive, highly typical sensitivity
Disadvantages: larger volumes, hard to see organisms in sediment, labour intensive - 26Describe the 30 min assay with Vibrio fischeri.- cells from a log phase culture
- simple saline medium; 1mL test solution, 5 concentrations + control in triplicate
- no lighting needed
- inhibition of luminescence after 30 min chemical exposure
- measure fluorescence in a fluorescence plate reader
- positive control: metals or antibiotics - 27What are the advantages/disadvantages of the assay?Advantages: fast, not labour intensive, good first cut diagnostic, can be lengthened to a 18h growth assay with the same endpoint
Disadvantages: insensitive to many contaminants, uptake limited, not representative of higher organisms - 28Describe avian toxicity testing.- commonly used in lab and field studies for industrial contaminants
- used for risk assessment of pesticides, chemicals and effluents
- endpoint: production of fertile, viable eggs
- acute oral toxicity: chemical placed into diet under light conditions that don't promote breeding, then breeding is promoted later
- plot EC10 for acute and subacute tests
- common species: northern bobwhite, japanese quail, mallard duck - 29What are some biotic variables that affect test outcomes?- test organism: variations between species
- life stage, size: developmental stages are more susceptible; larger animals less sensitive
- acclimation/acclimatization: modifications in biological functions over time (ex. tolerance)
- genetics: different populations of the same species can have variable sensitivity
- sex differences: endocrine disrupters impact reproductive systems differently - 30What are some abiotic variables that affect test outcomes?- temperature: added stress
- dissolved O2: added stress in low O2 conditions, oxygen radicals are a threat
- pH: metal toxicity decreases with pH, NH3 toxicity increases with pH
- water hardness: metals are more toxic in soft water
- light: increases toxicity of aromatics (PAHs)
- salinity - 31What are some negative and positive effects associated with chemicals?Negative:
- narcosis: membrane damage
- biochemical toxicity: enzyme inhibition
- ROS: oxidative damage
- endocrine toxicity: hormone mimic
- genotoxicity: mutation, replication inhibition
Positive:
- detoxification: degradation and excretion
- acclimation: defense responses - 32List metals that are metabolic (required) and non-metabolic.Metabolic: iron, calcium, zinc, selenium, copper, cobalt, manganese
Nonmetabolic: lead, cadmium, nickel, tin, mercury, silver - 33Describe Class A metals.- Complexes with O > N > S (oxygen seeking)
- Associates with carboxyls, carbonyls, alcohols, phosphates
- Targets phospholipids (cell membrane), nucleic acids (DNA, RNA), ATP and ADP - 34Describe Class B metals.- Complexes with S > N >> O (sulfur or nitrogen seeking)
- associates with sulphydryls, disuplhides, thioethers, and amines
- Targets amino acids, proteins, and free nucleotides - 35What are the functions of metals in metabolism?Enzyme cofactors:
- Fe: electron transport
- Zn: superoxide dismutase
- Mg/Mn: photosynthesis
- Cu: electron transport
- Ca: cell signalling
Structural components:
- Fe: hemoglobin, cell structure
- Zn: zinc fingers in transcription factors
- Ca: bone structure, cell structure - 36How can metals disturb metabolic functions?- divalent metals can inhibit ion pumps (ex. Ca)
- Cd can replace Cu in electron transport enzymes (displaces metal cofactors)
- metals can bind to nucleotide bases, results in mismatches and chromosomal damage
- impact on epithelial tissue - 37What are the negative impacts of Cu and Zn?- more of a problem in aquatic organisms than mammals
- toxicity threshold:
in soft water: 10-20 ug/L for Cu, 50-110 ug/L for Zn
in hard water: 30-100 ug/L in Cu, 1000-1500 ug/L in hard water
- Cu binds to DNA in between bases, inhibits photosynthesis in plants, inhibits ion pumps - 38What is the Reactive Oxygen Catalytic Mechanism?- catalytic mechanism available at lower concentrations
- ability to create O2-, H2O2, and hydroxyl radicals (least to most reactive)
- redox active metals can catalyze electron transfer from biomolecules to O2
- can damage lipids, protein, DNA and RNA - 39What is the BLM?- biotic ligand model: direct binding to biological receptors (membrane lipids, proteins, pumps, etc.)
- generally dominates at higher concentrations
- more likely to have acute effects - 40What is RCM?- catalytic production of ROS species
- generally dominates at lower concentrations
- more likely to have chronic effects - 41What are the impacts of Cd?- nonmetabolic
- Cd(2+) is the most important form
- acute toxicity through BLM: binds to SH groups on proteins to inhibit function
- inhibits plant growth
- causes kidney failure in mammals
- causes impaired reproduction in fish (1 ug/L) - 42What are the impacts of Pb on mammals?- nonmetabolic
- toxic form is inorganic Pb; exists in the form as an organometallic, organic gets removed inside the organism
- effect on mammals: accumulates in the liver and kidneys, then enters bloodstream and reduces RBC life span
- can cross the blood brain barrier and the placental barrier
- cumulative poison - 43What is the site of inhibition for Pb?Aminolaevulinic acid dehydratase (ALAD)
- enzyme in heme biosynthesis - 44What are the impacts of Pb on plants?Generally no impact - hard to mobilize from soils
- low concentrations will slow cell division in root tips
- higher concentrations will impair germination, growth, and photosynthesis through BLM
- LC50 = 1000-2000 ug/L - 45What are the effects of Hg?- toxic form is inorganic Hg, exists in the environment as an organometallic
- methyl Hg is very important
- crosslinks DNA and causes single stranded breaks --> cancerous
- affects the CNS and brain (methyl Hg)
- symptoms: sensory and motor skill impairment, anorexia, lethargy, visual impairment
- can cross into the placental blood barrier and affect fetuses - 46What are the toxic effects of mercury (Hg2+)?- can lead to neurological disorders in the brain (Mad Hatter's disease)
- MeHg specifically targets the CNS
- associates with cysteine in blood plasma (passes through via Met carriers) - 47What are the positive responses of metals?- enzymatic activities that consume O2- and H2O2
- superoxide dismutase: 2 O2- + 2H+ --> H202 + O2
- catalase: 2 H202 --> 2 H2O + O2
- glutathione peroxidase: 2GR(red) + H202 --> 2GR (ox) + 2H20
- metals cannot be metabolized; sequestered and/or excreted - 48What are metallothioneins?- family of low MW metal binding proteins
- regulates essential metals, protects against metal toxicity (ex. ROS)
- has a high Cys content, can bind 2 metals per MT
- expression induced by metals (stress related protein)
- can remove metals from other macromolecules in the cells - 49Define radiation. What are the two types of radiation?Radiation: energy that can be transferred from one body to another through a vacuum.
- nonionizing: light rays, radiowaves, etc.
- ionizing: high energy photons from radioactive nuclides - 50How does radiation inflict damage?alpha particles: P2N2 (nucleus pieces)
beta particles: electrons or positrons from nuclear decay
- alpha, beta, and gamma particles can penetrate matter and collide with electrons --> disrupts molecular bonds - 51What is the difference between ionization and excitation?- ionization: unstable molecule --> molecule can either recapture and electron to return to the original state, or break chemical bonds and react with other molecules
- excitation: excited molecule --> can return to the ground state (luminescence) or dissociate (damage) or transfer energy to another molecule (heat or damage) - 52What are the effects of radiation on organisms?Doses:
>1 Gy - radiation sickness from intestinal damage
> 3 Gy - skin blisters
>8 Gy - eventual death from indirect causes (infection)
>500 Gy - rapid death
- main risk from low doses in humans is cancer
- radiation at any dose can damage molecules - 53What are the properties of PAHs?- low water solubility, lipophilic
- relatively unreactive, unless activated
- photoactive
- stable and somewhat inert
- metabolized, do not biomagnify - 54How does PAH get activated?- photochemical activation: PAH absorbs solar UV radiation
- biochemical activation: transformation of PAHs through hydroxylation
- endocrine disruption: some oxyPAHs mimic hormones, induces cytochrome P450 - 55What is the difference between photosensitization and photomodification?photosensitization: simultaneous exposure of the organism and PAH to UV radiation
photomodification: pre-exposure of PAHs to UV, can occur inside or outside of the organism - 56What is the correlation between PAHs and liver carcinogenesis in fish?- high MW PAHs are a greater problem for mutagenesis
- PAH is oxidized in the liver and generally excreted, however some oxidized PAHs can attack DNA in liver cells
- do not biomagnify in fish due to cytochrome P450 oxidation followed by glutathione S transferase conjugation - 57What are the positive effects of PAH toxicity?- PAHs induce cytochrome P450 expression: Ah receptor induces liver P450IA1 at the transcriptional level
- 58What are PCBs?- polychlorinated biphenyls
- highly lipophilic
- mixture of 209 different congeners, can be coplanar or eclipsed
- more toxic in eclipsed form
- persistent in sediments - 59What are the negative effects of PCBs?- hydroxylated by cytochrome P450IA1, proceeds via epoxide intermediate
- if not metabolized, bioaccumulation occurs --> causes membrane damage, mutations, narcosis
- endocrine disrupters: altered P450 activity, mimics existing hormones
- causes prophyria: increased activity of aminolevulenic acid synthetase --> causes photosensitization - 60What are the properties of dioxins and furans?- highly lipophilic
- mixture of many possible congeners
- furans similar to dioxins - 61What are the negative effects of dioxins?- similar to PCBs
- causes liver necrosis and hemorrhaging
- teratogenic: mutagenic and carcinogenic
- acutely toxic
- potency of different dioxins is relations to Ah association/activation - 62What are the characteristics of pesticides and insecticides?- designed to kill
- environmental problem when it impacts non target organisms
- insecticides include organochlorines, organophosphates, carbamates - 63How are organochlorines toxic?- nerve poisons
- prevents closure of sodium channels
- immobilizes target species
- carcinogen, affects endocrine activity
- example: DDT - 64How are organophosphates toxic?- nerve poison
- inhibits acetylcholine esterase
- example: parathion - 65What are examples of natural toxic plant products?1. Nicotine: plant alkaloid
- targets aphids, nerve poison at acetylcholine receptor
2. Rotenoids: root extract
- electron transport inhibitor
3. Pyrethrums: chrysanthemum extract
- highly toxic to insects, nerve poison at ion channels - 66Describe the use of herbicides.- permanent removal of vegetation: high dose, nonselective --> usually use diuron or atrazine
- temporary removal of vegetation: nonpersistent and nonselective --> paraquat or glyphosate
- selective removal: usually use 2,4-D (a synthetic auxin selective for dicots) - 67How do triazines and ureas work?- inhibits photosystem II: competitive inhibitor at quinone binding site
- binds to QB site, prevents PQ from binding which inhibits photosynthesis - 68How does methyl viologen/paraquat work?- accepts electrons from Photosystem I, then passes them to O2 and creates a superoxide
- 69What does glyphosate inhibit?- inhibits metabolism
- inhibits the synthesis of aromatic amino acids (Shikimate pathway)
- inhibits 5-enolpyruvylshikimate-3-phosphate synthetase - 70What is a biomarker? What is the difference between biomarkers of effect and exposure?Any biological response to an environmental chemical at the individual level
- can be molecular, biochemical, morphological, etc.
- biomarkers of effect: demonstrates adverse effects on the organism
- biomarkers of exposure: indicates exposure on the organism, but doesn't give information about the degree of adverse effects - 71What is a bioindicator?Biological responses at higher organizational levels (population, community, ecosystem)
- 72What are some issues of biomarker usage?- need to know the mechanism of the biomarker being used
- response often occurs at a lower concentration than whole organism assays
- should be relatively easy to measure - 73How does the EROD assay work?- expose organism to control and contaminant for 1-4 days
- if invertebrate, isolate liver. For other organisms, take whole tissue/cells
- homogenize tissue for assay
- add ethoxy-resofurin and NADPH, incubate and assay increase in fluorescence - 74What are the advantages and disadvantages of the EROD assay?advantages: rapid, sensitive and logical response
disadvantages: only measures exposure of compounds that induce the Ah receptor - 75How is photosynthesis used as a biomarker?- biomarker for contaminant exposure
- assays for photosynthesis:
CO2 fixation - Calvin cycle
O2 evolution - electron transport
chlorophyll A fluoresence - photosystem II, electron transport - 76What are the advantages and disadvantages of using photosynthesis as a biomarker?advantages: measures impact, directly related to whole plant physiology, detects many classes of toxicants
disadvantages: equipment intensive, complex responses, no more sensitive than growth - 77How is gene expression used as a biomarker?- northern hybridization
- PCR techniques
- microarray techniques - 78What are the advantages/disadvantages of using gene expression as a biomarker?advantages: sensitive to low concentration, revealing of mechanism, molecular fingerprint
disadvantages: hard to connect to the mechanism of impact, labour intensive, open to artifacts - 79How are biomarkers validated?- assume molecular response: connect molecule endpoint to a biochemical response to a physiological response to a whole organism response
- kinetics of biomarkers should mirror kinetics of whole organism response
- should be able to detect the biomarker in a field trial under the same conditions as the environment - 80List the possible types of contaminants found in soil.1. petroleum hydrocarbons (PHC)
2. PAHs from petroleum, steel, and coal
3. chlorinated organics (PCBs, DDTs)
4. Pesticides from agriculture
5. Metals - steel production, industrial waste
6. Salt - agriculture, road salt, oil and gas - 81What are the possible contaminant remediation methods?- landfill disposal (any contaminant)
- soil incineration (for organics)
- chemical extraction (any contaminant)
- electrokinetic separation (metal/salt)
- soil flushing (any)
- land farming (small organics)
- bioremediation (organics)
- phytoremediation (any) - 82What is phytoremediation? What are its advantages?- the use of plants to remove contaminants from water, soil and air
- improves the natural structure/texture of soil
- suitable for most climates and regions
- restoration takes 2-3 years (reasonable)
- provides sufficient biomass for rapid remediation --> promotes high rhizosphere activity - 83What are the techniques involved in phytoremediation and what do they target?1. phytoextraction - metals, toxic inorganics
2. phytodegradation - organics that are mobile (ex. herbicides)
3. rhizodegradation - hydrophobic organics (PCB, PAH)
4. phytostabilization - vegetative caps, hydraulic barriers
5. natural attenuation - naturally occurring process - 84What is the phytoremediation process?Leaves:
1. volatilization
2. phytodegradation
3. chelation in leaves
In roots:
1. translocation from root symplast to xylem
2. chelation in roots
3. plant uptake from soil to root
4. rhizosphere processes
5. bioavailability particle (water) - 85What are PGPR? What do they do?- free living soil bacteria (stands for plant growth-promoting rhizobacteria)
- typically applied to seeds prior to planting
- decreases ethylene stress to the plant
- produces siderophores which help sequester iron
- helps solubilize phosphorus for the plant
- produces plant-like auxins which promote growth - 86How can PHCs be degraded through phytoremediation?- plant enzymes contain oxidases and hydrolases that can degrade contaminants
- microbial enzymes affect plant growth/physiology, can diminish ethylene stress
- exudates substrates that can stimulate microbial growth
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