Toxicant-Induced Cellular Dysfunction: Cellular Damage and Defense Mechanisms
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Questions and Answers

What is the result of covalent binding between a toxicant and a target molecule?

  • Electron transfer occurs
  • A reversible bond is formed
  • A toxicant-target molecule is termed an adduct (correct)
  • Hydrogen abstraction occurs

    • What type of compounds are abundant in biological systems and can participate in covalent binding?

  • Electrophilic compounds
  • Reactive oxygen species
  • Xenobiotics
  • Nucleophilic compounds (correct)

    • What is a potential consequence of covalent binding of toxicants to cellular proteins?

  • Stimulation of enzyme reactions
  • Inhibition of vital enzyme reactions (correct)
  • Alteration of protein structure
  • All of the above

    • What is the term for the original substance to which the host was exposed?

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

    Which type of interaction involves the transfer of electrons between a toxicant and its target molecule?

    <p>Electron transfer</p> Signup and view all the answers

    What is the result of the reaction between an electrophilic compound and a nucleophilic compound?

    <p>Covalent binding</p> Signup and view all the answers

    What is the consequence of covalent binding of toxicants to nucleic acids?

    <p>Inhibiting protein synthesis or inducing DNA mutations</p> Signup and view all the answers

    Which molecules are frequently involved in toxicity due to their exposure to reactive chemicals?

    <p>Endogenous molecules adjacent to sites of reactive metabolite formation</p> Signup and view all the answers

    What is the first target for reactive metabolites?

    <p>The enzyme that catalyzes their production</p> Signup and view all the answers

    What is required for a toxicant to react with a target molecule?

    <p>The target molecule must possess the appropriate reactivity and/or steric configuration</p> Signup and view all the answers

    What is the effect of some toxicants on protein target molecules?

    <p>They inhibit the function of protein target molecules</p> Signup and view all the answers

    What is the result of bifunctional electrophiles reacting with cytoskeletal proteins, DNA, or DNA with proteins?

    <p>Cross-linking of macromolecules</p> Signup and view all the answers

    What is the consequence of radicals converting proteins into reactive electrophiles?

    <p>Induction of cross-linking of macromolecules</p> Signup and view all the answers

    What is necessary to conclusively identify a target molecule as being responsible for toxicity?

    <p>All of the above</p> Signup and view all the answers

    What is the effect of tetrodotoxin and saxitoxin on the neuronal membrane?

    <p>They inhibit the opening of voltage-activated sodium channels</p> Signup and view all the answers

    What is the result of toxicants binding to tubulin or actin?

    <p>Impairing the assembly and/or disassembly of these cytoskeletal proteins</p> Signup and view all the answers

    What is the result of receptor activation in cells?

    <p>Altered gene expression and/or chemical modification of specific proteins</p> Signup and view all the answers

    What is the common modality of dysregulation of transcription?

    <p>Altered activation of transcription factors</p> Signup and view all the answers

    What is the result of xenobiotics facilitating phosphorylation of signal transduction proteins?

    <p>Promotion of mitosis and tumor formation</p> Signup and view all the answers

    What is the effect of phorbol esters on protein kinase C (PKC)?

    <p>Activation of PKC by mimicking diacylglycerol</p> Signup and view all the answers

    What is the result of Pb2+ on protein kinase C (PKC)?

    <p>Mimicking Ca2+, a physiologic activator of PKC</p> Signup and view all the answers

    What is the effect of activated PKC on mitogenic signaling?

    <p>Promotion of mitogenic signaling by starting a cascade</p> Signup and view all the answers

    What can be the result of xenobiotics influencing cellular activity in excitable cells?

    <p>Perturbation of ongoing cellular activity</p> Signup and view all the answers

    What can be the final endpoint of cellular or biochemical toxicity?

    <p>All of the above</p> Signup and view all the answers

    What is the effect of cross-linking on target molecules?

    <p>Spontaneous degradation and reactivity with adjacent molecules</p> Signup and view all the answers

    What can be the result of chemicals interfering with signal transduction?

    <p>Aberrant signal transduction and altered protein-protein interactions</p> Signup and view all the answers

    What is the result of severe cell damage?

    <p>Cell death</p> Signup and view all the answers

    What is the main difference between necrosis and apoptosis?

    <p>Necrosis involves a group of contiguous cells, while apoptosis is an individual cell death</p> Signup and view all the answers

    What is the result of a reduced production of cellular proteins in necrosis?

    <p>Changes in electrolyte gradient</p> Signup and view all the answers

    What is the term for the accumulation of lipids in the cytoplasmic vacuoles in necrosis?

    <p>Fatty accumulation</p> Signup and view all the answers

    What is the normal process in which cells have a finite lifespan and spontaneously die?

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

    What is the term for the fragments of cells that undergo apoptosis?

    <p>Apoptotic bodies</p> Signup and view all the answers

    What is the result of dysfunction of cell maintenance?

    <p>Cell death</p> Signup and view all the answers

    What is the energy currency of the cell?

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

    What is the result of impairment of oxidative phosphorylation?

    <p>Cell death</p> Signup and view all the answers

    What is the process that couples oxidation of hydrogen to water in the mitochondria?

    <p>Oxidative phosphorylation</p> Signup and view all the answers

    What is the primary organ responsible for excreting metals from the body?

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

    Which metal is known to be a potent nephrotoxicant?

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

    What is the effect of methylmercury on the nervous system?

    <p>It crosses the blood-brain barrier and enters the nervous system</p> Signup and view all the answers

    What is the result of xenobiotics binding to hormone receptors?

    <p>Stimulation of hormone-dependent processes</p> Signup and view all the answers

    Which estrogen receptor agonist is known to cause gynecomastia?

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

    What is the effect of chronic exposure to metal dust on the respiratory system?

    <p>All of the above</p> Signup and view all the answers

    What is the function of metal-binding proteins in the cell?

    <p>To decrease metal bioavailability</p> Signup and view all the answers

    Which type of metal compound is more likely to enter the nervous system?

    <p>Organic mercury compounds</p> Signup and view all the answers

    What is the result of metal inclusion bodies forming in the nucleus?

    <p>Unknown effects</p> Signup and view all the answers

    Which of the following metals is a known human carcinogen?

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

    What is the primary function of metallothionein (MT) in the body?

    <p>To regulate the intracellular bioavailability of certain metals</p> Signup and view all the answers

    What is the mode of action of carbamate and organophosphate insecticides?

    <p>Inhibition of cholinesterase</p> Signup and view all the answers

    What is the effect of acetylcholinesterase inhibition on nerve or muscle stimulation?

    <p>Prolonged, uncoordinated nerve or muscle stimulation</p> Signup and view all the answers

    What is the typical duration of acetylcholinesterase inhibition?

    <p>Minutes to permanent</p> Signup and view all the answers

    What is the primary cause of death in cases of cholinesterase inhibition?

    <p>Respiratory failure</p> Signup and view all the answers

    What is the mechanism of action of neonicotinoid insecticides?

    <p>Stimulation of acetylcholine receptors</p> Signup and view all the answers

    What is the function of acetylcholinesterase in the nervous system?

    <p>To hydrolyze acetylcholine into choline and acetate</p> Signup and view all the answers

    What is the effect of pyrethrin and pyrethroid binding to sodium channels?

    <p>Fixing the channels in an open state</p> Signup and view all the answers

    What is the mechanism of action of avermectins?

    <p>Activation of chloride channels</p> Signup and view all the answers

    What is the primary function of Na+K+ ATPases in nerve impulse transmission?

    <p>To actively transport sodium out of the cell</p> Signup and view all the answers

    What is the mechanism of action of chemicals in class D?

    <p>Inhibition of oxidative phosphorylation by direct inhibition of ATP synthase</p> Signup and view all the answers

    What is the effect of sustained elevation of intracellular Ca2+?

    <p>Inhibition of ATPase</p> Signup and view all the answers

    How do metals exert their toxicity?

    <p>By crossing the membrane and entering the cell</p> Signup and view all the answers

    What is the major site of toxic action for metals?

    <p>Interaction with enzymes</p> Signup and view all the answers

    How can metals inhibit enzymes?

    <p>All of the above</p> Signup and view all the answers

    What is the result of lead displacing zinc in the enzyme δ-aminolevulinic acid dehydratase (ALAD)?

    <p>Inhibition of the synthesis of heme</p> Signup and view all the answers

    What is the effect of Ca2+ on the citric acid cycle?

    <p>Activation of the citric acid cycle</p> Signup and view all the answers

    What is the result of Ca2+ activating nitric oxide synthase?

    <p>Formation of ONO2-</p> Signup and view all the answers

    What is the effect of xenobiotics on intracellular Ca2+ levels?

    <p>Increase in intracellular Ca2+ levels</p> Signup and view all the answers

    What is the effect of toxic metals on subcellular organelles?

    <p>Disruption of subcellular organelles</p> Signup and view all the answers

    What is the primary mechanism of neurotoxicity of DDT?

    <p>Inhibition of Na+K+ ATPases</p> Signup and view all the answers

    Which type of receptors are associated with chloride channels on the postsynaptic region of the neuron?

    <p>GABAA receptors</p> Signup and view all the answers

    What is the effect of GABAA receptor inhibition on nerve excitation?

    <p>Increased nerve excitation</p> Signup and view all the answers

    Which insecticides elicit acute neurotoxicity by inhibiting the GABAA receptor?

    <p>All of the above</p> Signup and view all the answers

    What is the primary mechanism of action of avermectins?

    <p>Binding to GABA-insensitive chloride channels</p> Signup and view all the answers

    Which compounds enhance the ability of gamma-aminobutyric acid to bind the GABAA receptor?

    <p>Both a and b</p> Signup and view all the answers

    What is the process by which energy is generated in the cell while molecular oxygen is consumed?

    <p>Cellular respiration</p> Signup and view all the answers

    Where does the process of cellular respiration occur?

    <p>Inner mitochondrial membrane</p> Signup and view all the answers

    What is the effect of rotenone on cellular respiration?

    <p>Inhibition of electron transfer at site 1</p> Signup and view all the answers

    What is a common symptom of toxicity resulting from the inhibition of cellular respiration?

    <p>Respiratory distress</p> Signup and view all the answers

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