Exam III 2016 KEY - F16 ETX 101 Exam III Student Number_KEY...

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F16 ETX 101 Exam III Student Number _____KEY_____________ Q1. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, dioxin) and related dioxin-like chemicals are highly toxic substances that are found in people and wildlife throughout the world. Name or very briefly describe TWO relevant physical and/or chemical properties of these chemicals that contribute to both their persistence and world-wide distribution. In other words, why does everyone have residues of dioxins and related dioxin like chemicals in their bodies? (8 points) Persistence in organisms and its world-wide distribution would be caused by: TCDDs stability (i.e., resistance to degradation (both biotic and abiotic)) and extreme hydrophobicity (which determines its storage in animals and partitioning into soil and sediment, which decreases its availability for degradation). Q2. What is the Ah receptor and why is it important in toxicology? (8 points) The Ah receptor is a chemical activated transcription factor that mediates the toxic and biological effects of dioxin and related chemicals. It is responsible for the induction of expression of numerous genes including that of several Phase I (cytochrome P450s) and Phase II enzymes. Numerous other important aspects to toxicology are also acceptable. Q3. There are three major categories of biomarkers that are used in toxicological research. Provide the following information for each biomarker: (18 points total) 1. The name of the specific biomarker. (2 points) 2. A brief definition or description of the specific biomarker. (3 points) 3. An example of this type of biomarker. (1 points) A. Biomarker of Exposure . Definition: Measurement of an exogenous substance or its metabolite, or the product of an interaction between a xenobiotic and some target molecule or cell - measured in a compartment within an organism (i.e., blood). Example: Hydroxylated metabolites of PCBs B. Biomarker of Effect . Definition: A measurable biochemical, physiological, behavioral or other alteration that can be recognized as associated with an established or possible health effect or disease resulting from toxicant exposure.
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