52 Questions
What is the result of the reaction of toxicants with target molecules?
Impaired cellular function
What is the effect of xenobiotics on gene expression?
Dysregulation of gene expression
What is the consequence of the destruction of target molecules?
Cellular dysfunction
How do xenobiotics interact with transcription factors?
By mimicking natural ligands
What is the result of the impairment of internal maintenance?
Sustained rise in Ca2+
What is the consequence of SH groups interfering with the template function of DNA?
DNA mispairing
What is the primary outcome of the reaction of the ultimate toxicant with the target molecule?
Injury of the target molecule itself, cell organelles, cells, tissue, and organs
What is a characteristic of target molecules that allows them to react with toxicants?
Possession of appropriate reactivity and/or steric configuration
Which type of reaction involves the binding of toxicants with receptors, ion channels, or enzymes?
Noncovalent binding
What is the term for the process by which toxicants alter target molecules in a way that is mechanistically related to the observed toxicity?
Adverse modification
Which type of toxicant reacts with target molecules through electron transfer?
Free radicals
What is the outcome of the dysfunction of target molecules due to toxicant exposure?
All of the above
Which amino acid contains sulfhydryl groups that are prone to oxidation?
Cysteine
What is the process by which damaged proteins are degraded in lysosomes?
Proteolysis
What is the primary function of glutathione (per)oxidase in the repair of lipids?
To reduce peroxidized lipids
What is the primary mechanism of direct repair of DNA damage?
Enzymatic reversal of damage
What is the primary difference between necrosis and apoptosis?
Necrosis involves cellular swelling, while apoptosis involves cellular shrinkage
What is the primary consequence of ATP depletion in a cell?
All of the above
What is the primary mechanism of action of cyanide as an inhibitor of ATP synthesis?
Inhibition of cytochrome oxidase
What is the primary role of Ca2+ in signal transduction?
Regulation of glutamate receptor
What is the primary consequence of sustained rises in intracellular Ca2+?
Activation of PKC
What is the primary function of Ca2+/ATPase in the cell?
To regulate Ca2+ levels in the cytoplasm
What is the reason for the exclusion of Ca2+ from the cytosol?
Its ability to easily precipitate with phosphates
What is the result of increased cytosolic Ca2+ on glycogen synthase?
It renders glycogen synthase inactive
What is the primary target for cell damage from ionizing radiation?
DNA
What is the result of radiation on cell membranes?
It changes the permeability of membranes to various molecules
What is the function of the electron transport system?
To generate ATP through the transport of electrons
What is the role of uncoupling proteins in brown fat?
To generate heat through non-shivering thermogenesis
What is the result of oxidative phosphorylation?
It generates ATP
What is the function of antioxidant defense systems?
To coexist with dioxygen
What is the result of oxidative stress?
It causes lipid peroxidation
What is the role of ROS in carcinogenesis?
They produce mutations in genes and proteins
What is the consequence of the reaction of hydroxylamine with C in DNA?
G-C pair becomes A-T pair
What is the result of the reaction of ethyl methanesulfonate with NH2 groups in DNA?
NH2 groups are converted to keto groups
What is the outcome of the deamination of cytosine and adenine in DNA?
GC→AT and A→G.C
What is the result of the interaction of indirect genotoxic chemicals with DNA?
Strand breaks or damage to the purine or pyrimidine rings
What is the category of mutation that occurs without the introduction of an exogenous mutagenic agent?
Spontaneous mutation
What is the result of the mechanism of base-analog substitution in DNA?
T is replaced by 5-bromoU which binds with G
What is the consequence of the process of inversion in a chromosome?
A segment of the DNA is inverted 180 degrees
What is the outcome of the reaction of a genotoxic substance with DNA that involves base substitution?
Point mutation
What is the result of the interaction of UV radiation with DNA?
Double strand breaks
What is the type of mutation that involves the addition or deletion of base sequences during DNA replication?
Frameshift mutation
What is the result of the activation of c-ras proto-oncogene to oncogene?
Abnormal growth of cells
What is the most frequent type of mutation in the p53 gene in cancer?
Transversions
What is the effect of alkylation at O-6 of G?
It leads to the formation of a tautomeric form that resembles A
What is the result of the interaction of intercalating agents with DNA?
It leads to the formation of frameshift mutations
What is the effect of HNO2 on DNA?
It deaminates bases
What is the result of the reactivity of nucleic acids with high pi bond order?
It is more reactive for addition reactions
What is the effect of UV radiation on DNA?
It leads to the formation of strand breaks
What is the category of carcinogens that irreversibly alter DNA?
Genotoxic carcinogens
What is the mechanism of initiation in carcinogenesis?
Reactivity of carcinogen with DNA
What is the effect of endocrine disruptors on wildlife?
All of the above
Test your knowledge on the reactions of ultimate toxicants with target molecules, including types of reactions, attributes of target molecules, and mechanisms of noncovalent and covalent binding. Learn about electrophiles, alkyl groups, and free radicals in toxicology.
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