Ch 6a

Question 1

Effects that begin at low levels of organization cascade up organization levels, give example

Answer 1

biochemical –> subcellular –> cellular –> tissue –> organ –> individual –> population –> community –>ecosystem –> landscape –> biosphere

Question 2

Why the interest in biomarkers and biochemical mechanisms (4)

Answer 2

1. understanding biochemical mechanisms may allow prediction of a new compound’s actions based on currently understood mechanisms
2. may allow effects of mixtures to be separated
3. may provide basis for understanding cellular or tissue effects
4. may provide an early warning system for exposure

Question 3

True or false - Indicator organism is the same as a sentinel species

Answer 3

TRUE

Question 4

define a biomarker

Answer 4

a biochemical, physiological, morphological or histological quality used to imply exposure to, or effect of a toxicant

Question 5

What are biomarkers used for

Answer 5

• used to indicate enough exposure for a sufficient time to generate a response
• usually detectable before higher level damage is measurable
• useful for monitoring cleanup

Question 6

What is an issue that can arise with biomarkers

Answer 6

showing how biomarkers are ecologically relevant can be an issue

Question 7

list some useful criteria for biomarkers

Answer 7

• measurable before higher level damage
• measurement should be rapid, inexpensive & easy
• should accommodate QA/QC measures
• should be specific for a toxin or family of toxins
• should be applicable to many sentinel species
• established relationship between biomarker changes & decreased individual fitness
• biological system should be well understood
• biomarkers can include elements of many different responses to toxic substances

Question 8

define a Sentinel species

Answer 8

Feral, caged or endemic species used in measuring & indicating contamination levels

• look for biomarkers in sentinel species
• can also be called indicator species

Question 9

True or false - Can detoxification reactions & their products act as biomarkers of exposure to toxins ?

Answer 9

TRUE

Question 10

Describe phase 1 reactions as biomarkers

Answer 10

depends on cytochrome P450 monooxygenase proteins

• known as a set of isoenzymes
• may have slightly different specificities but same basic reaction

Question 11

define an Isoenzyme

Answer 11

different forms of the same enzyme coded by different genes

Question 12

What is the general reaction of a phase 1 reaction as biomarkers ?
& what does it do ?

Answer 12

RH + NaDPH + O2 + H+ –> ROH + NADP+ + H2O

• usually increases solubility of xenobiotics
• may result in increased toxic activity rather than deactivation
• catalyzes hydroxylation reactions
• catalyzes epoxidation, dealkylation, oxidative deamination, oxidation, desulfurations, oxidative & reductive dehalogenation

Question 13

How may inductions of these phase 1 proteins as biomarker be studied ?

Answer 13

using DNA, mRNA or protein methods

Question 14

Name a way to detect proteins and list its steps

Answer 14

antibody assays such as ELISA

1. Homogenize tissue sample
2. Apply to ELISA plate
3. Detect with monoclonal antibody vs. marker protein
4. Detect 1~ antibody with 2~ antibody linked to a fluorescent marker or enzyme
5. Read fluorescence or colour change vs. standard curve

Question 15

Name another way to detect proteins and list its steps

Answer 15

Detection of mRNA or DNA with specific DNA probes

1. Bind mRNA or DNA to nitrocellulose membrane
2. label probe with fluorescent or radioactive nucleotides
3. Mix probe with membrane
4. detect specific binding

Question 16

What are 3 ways of quantifying the P450 activity by testing for activity of specific enzymes from this group.

Answer 16

1. AHH assay - benzo[a]