76 Questions
What is the result of covalent binding between a toxicant and a target molecule?
A toxicant-target molecule is termed an adduct
What type of compounds are abundant in biological systems and can participate in covalent binding?
Nucleophilic compounds
What is a potential consequence of covalent binding of toxicants to cellular proteins?
Inhibition of vital enzyme reactions
What is the term for the original substance to which the host was exposed?
Xenobiotic
Which type of interaction involves the transfer of electrons between a toxicant and its target molecule?
Electron transfer
What is the result of the reaction between an electrophilic compound and a nucleophilic compound?
Covalent binding
What is the consequence of covalent binding of toxicants to nucleic acids?
Inhibiting protein synthesis or inducing DNA mutations
Which molecules are frequently involved in toxicity due to their exposure to reactive chemicals?
Endogenous molecules adjacent to sites of reactive metabolite formation
What is the first target for reactive metabolites?
The enzyme that catalyzes their production
What is required for a toxicant to react with a target molecule?
The target molecule must possess the appropriate reactivity and/or steric configuration
What is the effect of some toxicants on protein target molecules?
They inhibit the function of protein target molecules
What is the result of bifunctional electrophiles reacting with cytoskeletal proteins, DNA, or DNA with proteins?
Cross-linking of macromolecules
What is the consequence of radicals converting proteins into reactive electrophiles?
Induction of cross-linking of macromolecules
What is necessary to conclusively identify a target molecule as being responsible for toxicity?
All of the above
What is the effect of tetrodotoxin and saxitoxin on the neuronal membrane?
They inhibit the opening of voltage-activated sodium channels
What is the result of toxicants binding to tubulin or actin?
Impairing the assembly and/or disassembly of these cytoskeletal proteins
What is the result of receptor activation in cells?
Altered gene expression and/or chemical modification of specific proteins
What is the common modality of dysregulation of transcription?
Altered activation of transcription factors
What is the result of xenobiotics facilitating phosphorylation of signal transduction proteins?
Promotion of mitosis and tumor formation
What is the effect of phorbol esters on protein kinase C (PKC)?
Activation of PKC by mimicking diacylglycerol
What is the result of Pb2+ on protein kinase C (PKC)?
Mimicking Ca2+, a physiologic activator of PKC
What is the effect of activated PKC on mitogenic signaling?
Promotion of mitogenic signaling by starting a cascade
What can be the result of xenobiotics influencing cellular activity in excitable cells?
Perturbation of ongoing cellular activity
What can be the final endpoint of cellular or biochemical toxicity?
All of the above
What is the effect of cross-linking on target molecules?
Spontaneous degradation and reactivity with adjacent molecules
What can be the result of chemicals interfering with signal transduction?
Aberrant signal transduction and altered protein-protein interactions
What is the result of severe cell damage?
Cell death
What is the main difference between necrosis and apoptosis?
Necrosis involves a group of contiguous cells, while apoptosis is an individual cell death
What is the result of a reduced production of cellular proteins in necrosis?
Changes in electrolyte gradient
What is the term for the accumulation of lipids in the cytoplasmic vacuoles in necrosis?
Fatty accumulation
What is the normal process in which cells have a finite lifespan and spontaneously die?
Apoptosis
What is the term for the fragments of cells that undergo apoptosis?
Apoptotic bodies
What is the result of dysfunction of cell maintenance?
Cell death
What is the energy currency of the cell?
ATP
What is the result of impairment of oxidative phosphorylation?
Cell death
What is the process that couples oxidation of hydrogen to water in the mitochondria?
Oxidative phosphorylation
What is the primary organ responsible for excreting metals from the body?
Kidney
Which metal is known to be a potent nephrotoxicant?
Cadmium
What is the effect of methylmercury on the nervous system?
It crosses the blood-brain barrier and enters the nervous system
What is the result of xenobiotics binding to hormone receptors?
Stimulation of hormone-dependent processes
Which estrogen receptor agonist is known to cause gynecomastia?
DES
What is the effect of chronic exposure to metal dust on the respiratory system?
All of the above
What is the function of metal-binding proteins in the cell?
To decrease metal bioavailability
Which type of metal compound is more likely to enter the nervous system?
Organic mercury compounds
What is the result of metal inclusion bodies forming in the nucleus?
Unknown effects
Which of the following metals is a known human carcinogen?
Arsenic
What is the primary function of metallothionein (MT) in the body?
To regulate the intracellular bioavailability of certain metals
What is the mode of action of carbamate and organophosphate insecticides?
Inhibition of cholinesterase
What is the effect of acetylcholinesterase inhibition on nerve or muscle stimulation?
Prolonged, uncoordinated nerve or muscle stimulation
What is the typical duration of acetylcholinesterase inhibition?
Minutes to permanent
What is the primary cause of death in cases of cholinesterase inhibition?
Respiratory failure
What is the mechanism of action of neonicotinoid insecticides?
Stimulation of acetylcholine receptors
What is the function of acetylcholinesterase in the nervous system?
To hydrolyze acetylcholine into choline and acetate
What is the effect of pyrethrin and pyrethroid binding to sodium channels?
Fixing the channels in an open state
What is the mechanism of action of avermectins?
Activation of chloride channels
What is the primary function of Na+K+ ATPases in nerve impulse transmission?
To actively transport sodium out of the cell
What is the mechanism of action of chemicals in class D?
Inhibition of oxidative phosphorylation by direct inhibition of ATP synthase
What is the effect of sustained elevation of intracellular Ca2+?
Inhibition of ATPase
How do metals exert their toxicity?
By crossing the membrane and entering the cell
What is the major site of toxic action for metals?
Interaction with enzymes
How can metals inhibit enzymes?
All of the above
What is the result of lead displacing zinc in the enzyme δ-aminolevulinic acid dehydratase (ALAD)?
Inhibition of the synthesis of heme
What is the effect of Ca2+ on the citric acid cycle?
Activation of the citric acid cycle
What is the result of Ca2+ activating nitric oxide synthase?
Formation of ONO2-
What is the effect of xenobiotics on intracellular Ca2+ levels?
Increase in intracellular Ca2+ levels
What is the effect of toxic metals on subcellular organelles?
Disruption of subcellular organelles
What is the primary mechanism of neurotoxicity of DDT?
Inhibition of Na+K+ ATPases
Which type of receptors are associated with chloride channels on the postsynaptic region of the neuron?
GABAA receptors
What is the effect of GABAA receptor inhibition on nerve excitation?
Increased nerve excitation
Which insecticides elicit acute neurotoxicity by inhibiting the GABAA receptor?
All of the above
What is the primary mechanism of action of avermectins?
Binding to GABA-insensitive chloride channels
Which compounds enhance the ability of gamma-aminobutyric acid to bind the GABAA receptor?
Both a and b
What is the process by which energy is generated in the cell while molecular oxygen is consumed?
Cellular respiration
Where does the process of cellular respiration occur?
Inner mitochondrial membrane
What is the effect of rotenone on cellular respiration?
Inhibition of electron transfer at site 1
What is a common symptom of toxicity resulting from the inhibition of cellular respiration?
Respiratory distress
This quiz covers the toxic effects of xenobiotics and their metabolites on host cells and tissues, leading to cellular dysfunction and injury. Learn about the different types of toxicants and how they interact with host molecules to cause harm. Understand the mechanisms of cellular defense against toxicant-induced damage.
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