Molecular Biology: DNA Mutations and Toxic Chemical Resistance
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Questions and Answers

What type of mutation occurs when a purine is substituted for another purine?

  • Translation
  • Transversion
  • Transcription
  • Transition (correct)

    • What is the main difference between toxicokinetically derived mechanisms and toxicodynamically derived mechanisms?

  • One is specific to humans, while the other is specific to insects
  • One is a short-term response, while the other is a long-term response
  • One alters the way chemicals are absorbed, while the other modifies target sites (correct)
  • One is a behavioral response, while the other is a molecular response

    • At what levels can protection against toxic chemicals occur?

  • At the molecular, genetic, cellular, tissue, organ, and whole organism levels (correct)
  • Only at the molecular and genetic level
  • Only at the whole organism level
  • Only at the cellular and tissue level

    • What is the result of a point mutation that substitutes a pyrimidine for another pyrimidine?

    <p>A transition</p> Signup and view all the answers

    Where did the earliest studies on tolerance and resistance mechanisms come from?

    <p>Insect/pesticide literature</p> Signup and view all the answers

    What is the purpose of the mechanisms of resistance used by organisms?

    <p>To avoid the effects of toxic substances</p> Signup and view all the answers

    What is the primary mechanism of toxicokinetically derived resistance?

    <p>Increased metabolic transformations of xenobiotics</p> Signup and view all the answers

    What is the result of sequestration of contaminants within cellular organelles or binding to proteins?

    <p>Toxicants are unable to exert their toxic effects</p> Signup and view all the answers

    What is an example of a storage site for organic xenobiotics?

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

    What is the function of the GSH thiol group in cellular detoxification?

    <p>Performing a nucleophilic attack on the target electrophile</p> Signup and view all the answers

    What is the mechanism of molecular repair of proteins involving thiol group oxidation?

    <p>Enzymatic reduction catalyzed by thioredoxin and glutaredoxin</p> Signup and view all the answers

    What is the primary mechanism of toxicodynamically derived resistance?

    <p>Alterations in xenobiotic-receptor interactions</p> Signup and view all the answers

    What is the function of molecular chaperons in protein repair?

    <p>To clamp down onto the exposed hydrophobic part and utilize ATP hydrolysis</p> Signup and view all the answers

    What is the result of non-silent point mutations within structural genes?

    <p>Target site modification</p> Signup and view all the answers

    What is the function of solute carrier proteins in elimination?

    <p>Mediating the vectorial transport of substrates into the cells</p> Signup and view all the answers

    What is the purpose of ubiquination of proteins?

    <p>To target proteins for degradation in the proteasome</p> Signup and view all the answers

    What is the role of glutathione peroxidase and glutathione reductase in lipid repair?

    <p>To repair peroxidized lipids</p> Signup and view all the answers

    What is the level at which repair mechanisms can occur?

    <p>At the molecular, cell, or tissue levels</p> Signup and view all the answers

    What is the result of increased metabolic transformations of xenobiotics?

    <p>Formation of less toxic or persistent forms</p> Signup and view all the answers

    Why is mitochondrial DNA more prone to damage than nuclear DNA?

    <p>Because it lacks efficient repair mechanisms</p> Signup and view all the answers

    What is the function of DNA photolyase in DNA repair?

    <p>To cleave adjacent pyrimidines dimerized by UV light</p> Signup and view all the answers

    What is the role of biotransformation in the elimination of toxicants?

    <p>Enhancing the elimination of toxicants</p> Signup and view all the answers

    What is the purpose of base excision repair in DNA?

    <p>To remove lesions that do not cause major distortion of the helix</p> Signup and view all the answers

    What is the result of unrepaired double-strand breaks in DNA?

    <p>Apoptosis or check of cell-cycle progression</p> Signup and view all the answers

    What is the likely function of the protein mentioned in the first sentence?

    <p>To repair broken DNA ends</p> Signup and view all the answers

    What is the role of O6-methylguanine-DNA methyltransferase (MGMT) in cells?

    <p>To protect cells against the toxic effects of alkylating agents</p> Signup and view all the answers

    What is the role of exonucleases or helicase activity in homologous recombination?

    <p>To produce a 3'-ended single-stranded tail</p> Signup and view all the answers

    What is the major component of the nonhomologous end-joining repair complex?

    <p>DNA-dependent protein kinase</p> Signup and view all the answers

    What is the purpose of chelating agents in the treatment of metal poisoning?

    <p>To form non-toxic complexes with metal ions</p> Signup and view all the answers

    What is the characteristic of a good chelating agent?

    <p>Ability to reach sites of storage and form non-toxic complexes</p> Signup and view all the answers

    What is the benefit of normal fluxes of proxidants in the cell?

    <p>They serve useful functions at the cellular and whole organism levels</p> Signup and view all the answers

    What is the main factor in oxidative stress injury?

    <p>Loss of control of endogenous oxidative events</p> Signup and view all the answers

    What is the percentage of O2 consumed by mammalian species that is delivered to mitochondria?

    <p>90%</p> Signup and view all the answers

    What is the byproduct of the four-electron reduction of O2 to H2O by the respiratory chain?

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

    What is the result of the incomplete reduction of O2 in mitochondria?

    <p>Formation of reactive oxygen species</p> Signup and view all the answers

    What is the most reactive and short-lived biological radical?

    <p>Hydroxyl radical</p> Signup and view all the answers

    What are the two main carotenoids that serve as provitaminA analogues and are effective antioxidants?

    <p>a- and P-carotene</p> Signup and view all the answers

    What is ascorbate capable of rapidly scavenging?

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

    What is the result of ascorbate reacting with other cellular prooxidants?

    <p>Prolonging the lifetime of a-TOH in the lipid phase</p> Signup and view all the answers

    What is the role of GSH-dependent reductase in ascorbate's antioxidant action?

    <p>Reducing dehydroascorbate back to ascorbate</p> Signup and view all the answers

    What is the characteristic of certain cancer chemotherapeutic agents such as nitrogen mustards?

    <p>They are direct-acting electrophiles</p> Signup and view all the answers

    What is the result of the conjugation of a biological reactive intermediate with GSH in bromobenzene metabolism?

    <p>Decrease in GSH concentration</p> Signup and view all the answers

    What is the primary mechanism of APAP metabolism at normal dose levels?

    <p>Sulfation and glucuronidation</p> Signup and view all the answers

    What is the role of the immune system in defending the body?

    <p>Distinguishing between self and non-self components</p> Signup and view all the answers

    What is the result of APAP overdosage?

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

    What is the function of GSH in protecting against APAP toxicity?

    <p>Conjugating with NAPQI</p> Signup and view all the answers

    What is the outcome of lipid peroxidation if termination reactions do not occur?

    <p>The process of lipid peroxidation will propagate, resulting in potentially high levels of oxidative stress.</p> Signup and view all the answers

    What is the role of detoxification of endogenously produced H2O2?

    <p>To maintain redox homeostasis</p> Signup and view all the answers

    What is the product of the dismutation reaction catalyzed by superoxide dismutases (SODs)?

    <p>H2O2</p> Signup and view all the answers

    Where is manganese SOD (Mn-SOD) primarily located?

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

    What is the function of catalase?

    <p>To reduce H2O2 to H2O and O2</p> Signup and view all the answers

    What is the role of glutathione peroxidase (GSH Px)?

    <p>To catalyze the reduction of organic peroxides</p> Signup and view all the answers

    What is the function of glutathione reductase (GR)?

    <p>To reduce GSSG to GSH</p> Signup and view all the answers

    What is the characteristic of small molecule antioxidants?

    <p>They can act by scavenging oxidants or chelating transition metal ions</p> Signup and view all the answers

    What is the role of vitamin E in cells?

    <p>To scavenge a wide array of ROS</p> Signup and view all the answers

    What is the role of ubiquinol Q10?

    <p>To act as a potent antioxidant in lipoproteins and other lipid membranes</p> Signup and view all the answers

    What is the primary function of macrophages in the innate immune response?

    <p>To engulf and destroy infectious agents and foreign particles</p> Signup and view all the answers

    What is the main difference between innate and acquired immune responses?

    <p>Innate responses are rapid but incomplete, while acquired responses are slower but more definitive</p> Signup and view all the answers

    What type of cells are eosinophils particularly effective against?

    <p>Helminthic parasites</p> Signup and view all the answers

    What is the role of cytokines in the immune system?

    <p>To regulate the activation, maturation, differentiation, and mobilization of immune cells</p> Signup and view all the answers

    What is the primary function of neutrophils in the innate immune response?

    <p>To engulf and destroy infectious agents and foreign particles</p> Signup and view all the answers

    What is the term for the process of enhancing phagocytosis by binding antibodies to molecules on the surface of microbes or other targets?

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

    What is the primary function of dendritic cells in the immune system?

    <p>To present antigens to T cells</p> Signup and view all the answers

    What is the term for the increased flow of blood to a site of inflammation, accompanied by increased permeability of capillaries?

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

    What is the primary function of the thymus in the immune system?

    <p>To differentiate T lymphocytes</p> Signup and view all the answers

    What is the term for the localized aggregates of immune cells in the lung, gut, and skin?

    <p>BALT, GALT, SALT</p> Signup and view all the answers

    What is the main function of natural killer cells in the innate response?

    <p>To lyse certain types of tumor cells and virally infected cells</p> Signup and view all the answers

    What is the primary function of type I interferons in the innate response?

    <p>To inhibit viral replication and increase the lytic potential of NK cells</p> Signup and view all the answers

    What is the role of pattern recognition receptors in the innate response?

    <p>To recognize features common to many pathogens and initiate an inflammatory response</p> Signup and view all the answers

    What is the primary function of the complement system in the innate response?

    <p>To facilitate phagocytosis and pathogen membrane lysis</p> Signup and view all the answers

    What is the role of macrophages in the acquired immune response?

    <p>To process and present antigens to T lymphocytes</p> Signup and view all the answers

    What is the function of the T-cell antigen receptor (TCR)?

    <p>To recognize and bind to proteolytically processed short peptide fragments</p> Signup and view all the answers

    What is the difference between Class I and Class II MHC molecules?

    <p>Class I MHC presents peptides derived from proteins produced within the cell, while Class II MHC presents peptides derived from proteins taken up by the cell</p> Signup and view all the answers

    What is the role of protein-tyrosine phosphorylation in T-cell activation?

    <p>It is important in the initiation of cellular responses that follow TCR recognition of the MHC-antigen complex</p> Signup and view all the answers

    What are the second messengers involved in the signaling pathways that lead to T-cell activation?

    <p>Inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG)</p> Signup and view all the answers

    What is the role of cytokines in the initiation of inflammatory responses?

    <p>They are important in the initiation of inflammatory responses and help to mobilize immune cells to the site of injury</p> Signup and view all the answers

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