Biotransformation of Toxicants Quiz
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Questions and Answers

What type of dose-response relationship is used to examine the mechanism of interaction between a toxicant and a biological system?

  • Cumulative / Accumulated
  • Quantic or population-based
  • Graded or individual (correct)
  • Frequency

    • Which type of dose-response graph represents the cumulative sum of responses from lower to higher doses?

  • Frequency
  • Graded or individual
  • Cumulative / Accumulated (correct)
  • Probit

    • What does the vertical axis in a dose-response graph represent?

  • Population response
  • In vivo or in vitro response (correct)
  • Logarithmic scale
  • Dose in mg/kg

    • Which type of pharmaceutical graph is used when the responses of test organisms follow a normal distribution?

    <p>Probit</p> Signup and view all the answers

    In which type of dose-response relationship are different doses administered to observe the population response characterized by 'all or none'?

    <p>Quantic or population-based</p> Signup and view all the answers

    What does the horizontal axis in a dose-response graph represent?

    <p>Dose in mg/kg</p> Signup and view all the answers

    What is the primary focus of descriptive toxicology?

    <p>Quantitative toxicity testing of chemicals</p> Signup and view all the answers

    Which subdiscipline of modern toxicology delves into the underlying molecular basis of toxicants' impact on organisms?

    <p>Mechanistic toxicology</p> Signup and view all the answers

    What characterizes hazardous waste according to the text?

    <p>Potential for causing disease and death</p> Signup and view all the answers

    What is the main goal of regulatory toxicology?

    <p>Determining legal uses of specific chemicals</p> Signup and view all the answers

    Which discipline contributes to an understanding of toxicology by focusing on the effects of toxins on embryos and fetuses?

    <p>Developmental Toxicology</p> Signup and view all the answers

    What is the main concern addressed by environmental toxicology as mentioned in the text?

    <p>Predicting effects on populations and ecosystems</p> Signup and view all the answers

    What is the branch of science that deals with the study of poisons or toxicants?

    <p>Toxicology</p> Signup and view all the answers

    Which of the following is NOT one of the time-dependent processes related to toxicants according to the text?

    <p>Metabolism</p> Signup and view all the answers

    Toxicodynamics examines the mechanisms by which toxicants produce unique cellular effects within the organism. What are some components of these mechanisms?

    <p>Changes to the cell's plasma membrane</p> Signup and view all the answers

    Which component is NOT typically considered in toxicity testing according to the text?

    <p>Age of the test organism</p> Signup and view all the answers

    What is lipid peroxidation, as mentioned in the text as a component of toxicity testing?

    <p>Oxidation of fatty acids leading to cell death</p> Signup and view all the answers

    In toxicity testing, what advantage do logarithmic doses have over linear doses?

    <p>They maximize the range of doses tested while minimizing the possibility of missing small doses that could represent the response threshold.</p> Signup and view all the answers

    What are the most important factors affecting the likelihood of a xenobiotic being absorbed?

    <p>Route of exposure, concentration of the substance, and chemical and physical properties</p> Signup and view all the answers

    Which factor is NOT considered important in determining xenobiotic absorption?

    <p>Intensity of the toxic effect</p> Signup and view all the answers

    What is the role of cell membranes in xenobiotic absorption?

    <p>They form formidable barriers to prevent entry of xenobiotics into body tissues</p> Signup and view all the answers

    Which route of exposure/absorption is considered an important route for many pharmaceuticals?

    <p>Gastrointestinal (GI) tract</p> Signup and view all the answers

    What type of tail do lipid molecules in cell membranes possess?

    <p>Lipophilic</p> Signup and view all the answers

    Which statement best describes the movement of xenobiotics through cell membranes?

    <p>Xenobiotics must cross several cell membranes to move within and between different areas of the body</p> Signup and view all the answers

    What is the primary function of cell membranes in the body?

    <p>To act as a major defense that prevents foreign substances from entering body tissues</p> Signup and view all the answers

    Lipinski's rule of five indicates poor absorption if which criteria are violated?

    <p><strong>MW &gt; 500 Da</strong></p> Signup and view all the answers

    Lipid solubility plays a key role in xenobiotic absorption due to its attraction to:

    <p><strong>Non-polar substances</strong></p> Signup and view all the answers

    Chemical and physical properties are important factors affecting xenobiotic absorption; which property directly affects absorption by being attracted to lipid-soluble substances?

    <p><strong>Lipid solubility</strong></p> Signup and view all the answers

    Which type of toxic responses include CNS damage, carcinogenesis, mutagenesis, and teratogenesis?

    <p>Irreversible toxic responses</p> Signup and view all the answers

    What determines the reversibility of toxicity damage?

    <p>The length of exposure</p> Signup and view all the answers

    Which type of cell membrane contains many pores and is found in kidney cells and liver cells?

    <p>Type 3</p> Signup and view all the answers

    What type of toxicity occurs when adverse effects take years to appear following exposure to a toxicant?

    <p>Delayed toxicity</p> Signup and view all the answers

    Which component of the cell membrane is very low in mitochondria?

    <p>Cholesterol</p> Signup and view all the answers

    In what type of tissue might rapidly regenerating tissue only suffer from reversible toxic responses?

    <p>Liver tissue</p> Signup and view all the answers

    Which type of exposure results in local toxicity?

    <p>Exposure to ingested toxicants</p> Signup and view all the answers

    Which type of toxicity is restricted only at the initial site of exposure to the toxicant?

    <p>Localized toxicity</p> Signup and view all the answers

    What affects the absorption of toxicants across cell membranes?

    <p>The protein-to-lipid ratio</p> Signup and view all the answers

    Which type of toxicant undergoes biotransformation in the liver if taken orally?

    <p>Organophosphates</p> Signup and view all the answers

    Which system is responsible for draining excess fluid from the tissues in the body?

    <p>Lymphatic system</p> Signup and view all the answers

    What is the primary determinant of a toxicant's rate of distribution to organs or tissues?

    <p>Blood flow and diffusion rate</p> Signup and view all the answers

    If a toxicant accumulates at a site other than the target organ, it may be viewed as a protective process because?

    <p>The plasma levels of the toxicant decrease</p> Signup and view all the answers

    Which factor influences the distribution of toxicants by determining the volume in which the amount of drug would need to be uniformly dissolved?

    <p>Volume of distribution (Vd)</p> Signup and view all the answers

    How does a chemical with distribution only to the plasma compartment affect its volume of distribution (Vd)?

    <p>High plasma concentration and low Vd</p> Signup and view all the answers

    What facilitates the distribution of xenobiotics that are protein-bound across cell membranes?

    <p>Specialized transport across the plasma membrane</p> Signup and view all the answers

    What determines the final distribution of a xenobiotic in various tissues of the body?

    <p>&quot;Barriers&quot; slowing down toxicant entrance</p> Signup and view all the answers

    Why may some toxicants selectively accumulate in certain parts of the body?

    <p>Due to their inability to cross cell membranes easily</p> Signup and view all the answers

    Which mechanism allows for toxicants to be released into circulation as they are eliminated?

    <p>Storage depots equilibrium with free toxicant fraction in plasma</p> Signup and view all the answers

    What facilitates the distribution of xenobiotics that are protein-bound across cell membranes?

    <p>Specialized transport across the plasma membrane</p> Signup and view all the answers

    What does it mean when a toxicant is considered more potent?

    <p>It produces a response at a lower dose compared to another toxicant</p> Signup and view all the answers

    What does a higher efficacy of a toxicant indicate?

    <p>The dose-response relationship continues over a greater range of doses</p> Signup and view all the answers

    What is the margin of safety (TI) used to express?

    <p>The range of doses between non-effective dose and lethal dose</p> Signup and view all the answers

    Which type of toxicity involves irreversible cellular changes that lead to long-lasting symptoms?

    <p>Chronic toxicity</p> Signup and view all the answers

    What is the significance of a large LD01/ED99 ratio for pharmaceuticals?

    <p>It shows the drug can be therapeutic at low doses compared to lethal doses</p> Signup and view all the answers

    What type of curve suggests a toxicant of high potency?

    <p>A steep curve at a smaller dose</p> Signup and view all the answers

    Which type of channels can permit the entry of cations such as lead, barium, or strontium?

    <p>Voltage-gated calcium channels</p> Signup and view all the answers

    What type of interactions primarily occur during protein-ligand interactions in plasma proteins?

    <p>Hydrophobic forces, hydrogen bonding, and van der Waals forces</p> Signup and view all the answers

    What does it mean when dose–response curves exhibit nontraditional shapes?

    <p>'Hormetic effects' are observed</p> Signup and view all the answers

    What is implied by intersecting or crossed sigmoidal lines on cumulative dose-response graphs?

    <p>'Mixed or reversed toxicity relationship'</p> Signup and view all the answers

    Which organ likely concentrates more toxicants than all other organs combined?

    <p>Liver</p> Signup and view all the answers

    What does chronic toxicity result from?

    <p>Repeated exposures of less than a lifetime</p> Signup and view all the answers

    Why is the first-pass effect important in toxicology?

    <p>To allow immediate detoxification by the liver</p> Signup and view all the answers

    What is the purpose of determining the margin of safety from two toxicity studies like an ED and LD study?

    <p>To determine the range between effective and lethal doses</p> Signup and view all the answers

    Which type of storage depot lowers the concentration of a toxicant in the target organ?

    <p>Adipose tissue</p> Signup and view all the answers

    What is the major protein in plasma responsible for binding many different compounds?

    <p>Albumin</p> Signup and view all the answers

    Which type of channels mediate the influx of arsenide?

    <p>Aquaporins</p> Signup and view all the answers

    What type of barrier do brain capillaries lack and are joined by tight junctions?

    <p>Tight junctions</p> Signup and view all the answers

    What phenomenon takes place between the bone surface and extracellular fluid in contact with it for toxicant deposition and reversible storage?

    <p>Surface chemistry phenomenon</p> Signup and view all the answers

    What is the most common way that xenobiotics cross cell membranes?

    <p>Passive diffusion</p> Signup and view all the answers

    Which mechanism involves the movement of molecules down a concentration gradient without requiring metabolic energy?

    <p>Facilitated diffusion</p> Signup and view all the answers

    What type of transport can be inhibited by a metabolic poison and may be saturated at high substrate concentrations?

    <p>Active transport</p> Signup and view all the answers

    In which mechanism do water-soluble molecules pass through small aqueous pores, allowing the movement of molecules of 50-60k MW?

    <p>Passive diffusion</p> Signup and view all the answers

    Which process requires ATP, produces vesicles, and may fuse with lysosomes?

    <p>Endocytosis</p> Signup and view all the answers

    What is the function of a sodium-potassium pump in terms of ion movement?

    <p>3Na+ out of the cell, 2K+ into the cell</p> Signup and view all the answers

    What is the statistic used to represent the distance of test organisms' responses from the mean?

    <p>Standard deviation</p> Signup and view all the answers

    If a toxicant has a small standard deviation compared to another toxicant, what does this indicate about the dose-response relationship?

    <p>The toxicant with the small SD has a narrower range of doses yielding responses.</p> Signup and view all the answers

    What is the term used to describe the dose at which the first test organism responds on a cumulative dose-response graph?

    <p>Threshold dose</p> Signup and view all the answers

    Which term refers to doses on the left side of the threshold dose where no responses are observed?

    <p>Subthreshold doses</p> Signup and view all the answers

    At what percentage level does the mean response occur on a cumulative dose-response graph?

    <p>50%</p> Signup and view all the answers

    What is observed on the right side of a cumulative dose-response graph when doses increase beyond a certain point?

    <p>Ceiling effect</p> Signup and view all the answers

    Which term represents the dose resulting in the death of test organisms?

    <p>Lethal dose (LD)</p> Signup and view all the answers

    What is the primary factor that determines the toxicity manifested by a xenobiotic in the body?

    <p>The concentration in plasma proteins</p> Signup and view all the answers

    Why might a highly lipophilic toxicant concentrated in body fat be less severe in toxicity in an obese person than a lean individual?

    <p>Its concentration is lower in the target organ due to storage in fat</p> Signup and view all the answers

    Which organ is mentioned as having a high capacity for binding various chemicals, potentially concentrating more toxicants than all other organs combined?

    <p>Liver</p> Signup and view all the answers

    What characterizes the skeletal uptake of xenobiotics, particularly with regard to deposition and storage in bone?

    <p>It can be dynamic and may not always be detrimental</p> Signup and view all the answers

    What is the primary driving force behind protein-ligand interactions that bind toxicants to plasma proteins?

    <p>Hydrophobic forces</p> Signup and view all the answers

    How do plasma proteins bound to toxicants interact with capillary walls?

    <p>The proteins and bound toxicants cannot cross capillary walls</p> Signup and view all the answers

    What is a major anatomical reason why some toxicants do not readily enter the CNS?

    <p>High protein concentration in the interstitial fluid of the CNS</p> Signup and view all the answers

    How do glial cell processes (astrocytes) affect toxicant entry into the CNS?

    <p>Act as barriers to toxicants entering the CNS</p> Signup and view all the answers

    In what way is the placental barrier similar to the blood-brain barrier?

    <p>Both lack pores between cell layers</p> Signup and view all the answers

    What role do lipids in the plasma membranes play in the placental barrier?

    <p>Limit the entry of water-soluble toxicants</p> Signup and view all the answers

    How does the protein concentration in the interstitial fluid of the CNS differ from other body fluids?

    <p>It prevents diffusion of polar compounds</p> Signup and view all the answers

    What is the primary function of glial cell processes (astrocytes) surrounding capillaries in the CNS?

    <p>Prevent diffusion of water-soluble toxicants</p> Signup and view all the answers

    What is the primary function of the loop of Henle in the kidney?

    <p>To reabsorb water from the filtrate</p> Signup and view all the answers

    Which of the following toxicants undergo reabsorption by renal tubules into the peritubular capillaries?

    <p>Acetaminophen</p> Signup and view all the answers

    What characterizes the proximal convoluted tubule in the kidney in terms of toxicant reabsorption?

    <p>Reabsorption of sodium and sulfate ions</p> Signup and view all the answers

    Which component of the nephron is responsible for being the charge/size selective site of filtration?

    <p>Glomerulus</p> Signup and view all the answers

    What is the main function of the descending tubule in the kidney nephron?

    <p>Reabsorption of water from the filtrate</p> Signup and view all the answers

    In kidney toxicity, which of the following chemicals is known to be filtered through renal corpuscles and secreted across tubular epithelium?

    <p>MTBE (gasoline additive)</p> Signup and view all the answers

    Which enzyme is primarily found in the ER, cytoplasm, and mitochondria?

    <p>Microsomal Flavin-Containing Monooxygenase</p> Signup and view all the answers

    What is the primary role of Cytochrome P-450?

    <p>Oxidation of drugs and xenobiotics</p> Signup and view all the answers

    Which enzyme is responsible for oxidizing tertiary amines to N oxides?

    <p>Mixed Function Oxidase 3</p> Signup and view all the answers

    What is the major function of Microsomal Flavin-Containing Monooxygenase?

    <p>Detoxify xenobiotics via oxidation</p> Signup and view all the answers

    Which enzyme is localized in the soluble fraction of the liver, kidney, and lungs?

    <p>Alcohol dehydrogenase</p> Signup and view all the answers

    What is the primary product of the first detoxification stage of benzene?

    <p>Epoxide</p> Signup and view all the answers

    What is the primary role of NADPH Cytochrome P-450 reductase?

    <p>Transfer electrons to Cytochrome P-450</p> Signup and view all the answers

    What property do biotransformed metabolites usually acquire compared to the original toxicant?

    <p>They become more hydrophilic</p> Signup and view all the answers

    Which enzyme type is primarily associated with phase II reactions in the metabolism of xenobiotics?

    <p>Cytosolic enzymes</p> Signup and view all the answers

    Which organs have a medium capacity for biotransformation processes?

    <p>Intestines, kidneys, and lungs</p> Signup and view all the answers

    In phase I of xenobiotic metabolism, what is the primary effect of introducing a polar group into the molecule?

    <p>Increasing water solubility</p> Signup and view all the answers

    Which cells possess a limited ability for biotransformation processes?

    <p>Hepatocytes and skin cells</p> Signup and view all the answers

    What can occur in some cases during xenobiotic metabolism that leads to a sequence termed an activation mechanism?

    <p>'Activation' mechanism producing more toxic intermediates or products</p> Signup and view all the answers

    'Microsomal enzymes are associated with which phase of xenobiotic metabolism?'

    <p>'Phase I reactions'</p> Signup and view all the answers

    'Which bacterial population has a significant impact on biotransformation in the body?'

    <p>'More than 400 bacterial species'</p> Signup and view all the answers

    'Which factor can impair an individual's capacity to biotransform xenobiotics?'

    <p>'Nutritional status'</p> Signup and view all the answers

    'Where do most biotransformation reactions occur at the subcellular level?'

    <p>'Endoplasmic reticulum'</p> Signup and view all the answers

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