Quiz
BCM-FINAL, PT 1
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Perguntas do quiz (52)
1Which of the following statements is FALSE regarding the binding of estradiol to the estrogen receptor?
- AThe alcohol and phenol groups of estradiol are important hydrogen bonding groups when estradiol binds to the binding site.
- BThe aromatic ring is not important in the binding process.
- CThe hydrophobic skeleton of the molecule forms hydrophobic and van der Waals interactions with the binding site.
- DThe binding site into which estradiol fits is spacious except for the region accepting the aromatic ring.
2Which of the following statements is not true regarding the actions of the estrogen receptor?
- ABinding of estradiol causes dimerization of the receptor.
- BBinding of estradiol causes a conformational change in the receptor.
- CA helical section of the receptor protein shifts position to seal estradiol into the binding site and reveals a hydrophobic region called the deactivating function region.
- DA coactivator protein binds to complete a nuclear translation factor.
3In the absence of hormone, estrogen receptor is not bound to DNA but to Hsp90. Estrogen binding displaces the receptor from Hsp90 and allows the formation of receptor dimers, which bind DNA and stimulates gene transcriptions.
- AVerdadeiro
- BFalso
4Which of the following statements is the closest description of Phase I metabolism?
- AReactions which add a polar molecule to a functional group already present on a drug or one of its metabolites.
- BReactions which as a polar functional group to a drug.
5Which of the following statements is the closest description of Phase II metabolism?
- AReactions which add a polar molecule to a functional group already present on a drug or one of its metabolites.
- BReactions which as a polar functional group to a drug.
6Which of the following enzymes is not involved in catalyzing a Phase I metabolic reaction?
- AFlavin-containing monooxygenase
- BMonoamine oxidases
- CGlucuronltransferase
- DEsterases
7Where in the cell is cytochrome P450 located?
- AMitochondrial inner membrane
- BCytosol
- CMitochondrial matrix
- DEndoplastmic reticulum
8All of the following are detoxifying agents, except:
- AGlycine
- BGlutathione
- CGlucuronic acid
- DGlycogen
9All of the following are true for cytochrome P450, except:
- AIs also called mixed function oxidase
- BUses NADPH
- CAssociated with smooth endoplasmic reticulum
- DIs an allosteric enzyme
10All of the following compounds are detoxified by sulfation, except:
- AIndole
- BPhenol
- CCresol
- DBenzoic acid
11All of the following are correct about a molecule designated as a cytochrome P450 except:
- AIt contains a heme as a prosthetic group
- BIt catalyzes the hydroxylation of a hydrophobic substrate
- CIt may accept electrons from NADPH
- DIt undergoes a change in the heme iron upon binding a substrate
- EIt comes from the same gene family as all other cytochrome P450
12Flavoproteins are usually intermediates in the transfer of electrons from NADPH to cyt P450 because:
- ANADPH cannot enter the membrane.
- BFlavoproteins an accept two electrons from NADPH and donate them one at a time to cytP450.
- CThey have a more negative reduction potential than NADPH so accept electrons more readily.
- DAs proteins, they can bind to cyt P450 while the nonproteins NADPH cannot.
- EThey contain iron-sulfur centers.
13Benzo[a]pyrene, a xenobiotic produced by combustion of a variety of substances:
- AInduces the synthesis of cytochrome P450.
- BUndergoes epoxidation by a cytochrome P450.
- CIs converted to a potent carcinogen in animals by cytochrome P450.
- DWould be rendered more water-soluble after the action of cytochrome P450.
- EAll of the above
14Which medication(s) should not be co-administered with grapefruit juice?
- AImmune suppressant agent (cyclosporine A)
- BWarfarin (anticoagulant)
- CStatin (lovastatin)
- DCalcium channel blocker (felodipine)
- EAll of the above
15An adult patient has been taking a drug (Drug A) that is highly metabolized by the cytochrome P450 system. He has been on this medication for 6 months. At this time, he is started on a herbal remedy that is an inducer of cytochrome P450 system. You should monitor this patient for:
- AIncreased therapeutic effects of Drug A
- BIncreased adverse effects of herbal remedy
- CDecreased therapeutic effects of Drug A
- DDecreased therapeutic effects of herbal remedy
16A 25-year-old male is seen in the hospital Emergency Department. He is disoriendted, but states that he has had nausea, vomiting and abdominal pain since he took “too many pain pills.” Upon examination, his eyes appear yellow. Laboratory tests indicate abnormal liver function (as determined by measurements of serum and bilirubin and liver-associated enzymes in the blood). In addition to gastric lavage, what is the appropriate treatment?
- AN-acetyl cysteine
- BAtropine
- CVitamin K
- DAlbumin via parenteral administration
- EFluphenazine
17The enzyme NADPH-adrenodoxin reductase is associated with which of the following systems
- AMitochondrial P450
- BER cytochrome P450
- CNeuronal nitric oxide synthase
- DAcetylcholine esterase
- EInducible NOS
18Indicate which of the following statements concerning Phase I metabolic drug reactions are correct:
- AAddition of a glucuronyl group is an example of a Phase I reaction
- BA major source of Phase I reactions is the cytochrome P450 enzyme system located in the liver smooth endoplasmic reticulum
- CThe products of Phase I reactions are usually more lipid soluble than the parent drug.
- DAddition of a glucuronyl group is an example of a Phase I reaction AND a major source of Phase I reactions is the cytochrome P450 enzyme system located in the liver smooth endoplasmic reticulum
- EA major source of Phase I reactions is the cytochrome P450 enzyme system located in the liver smooth endoplasmic reticulum AND the products of Phase I reactions are usually more lipid soluble than the parent drug.
19____ is responsible for the metabolism of the largest number of drugs.
- ACYP2D6
- BCYP3A4
- CCYP2E1
- DCYP1A2
20When St. John’s wort and irinotecan are ingested concurrently significant decreases in plasma concentration of irinotecan can occur.
- AVerdadeiro
- BFalso
21DNA ligase uses the energy of ATP to close nicks in DNA and this involves a mechanism which includes
- AAn AMP in a phospho-ester linkage to the 5’-hydroxyl at one side of the nick
- BAn AMP in a phosphor-anhydride linkage to the 5’-hydroxyl at one side of the nick
- CAn AMP in a phosphor-anhydride linkage to the side-chain of a tyrosine in DNA ligase
- DAn AMP in a phosphor-ester linkage to the 3’-hydroxyl at one side of the nick
- EA linkage of the side-chain of a tyrosine in DNA ligase to the 5’-phosphate at one side of the nick
22Cells normally delay replication until DNA damage and replication errors have been repaired because
- ADNA polymerase cannot function when the DNA is damaged
- BReplication of damage or mismatched DNA results in mutations
- CIt is not possible to do repair and replication at the same time
- DSome repair may require recombination, and that cannot be done during replication
23All of the following are correct about a Cytochrome P450 enzyme except:
- AIt contains a heme as a prosthetic group
- BIt catalyzes the hydroxylation of a hydrophobic substrate
- CIt may accept electrons from a substance such NADPH
- DIt undergoes a change in the heme iron upon binding a substrate
- EIt comes from the same gene family as all other Cytochrome P450
24Genetic polymorphism in genes for cytochrome P450:
- ACould cause an individual to metabolize poorly certain drugs
- BCould cause an individual to metabolize certain drugs more rapidly than normal
- CCould cause a specific ethnic group to experience more effects with certain drugs
- DAll of the above
25NADHP-cytochrome P450 reductase:
- AUses both FAD and FMN as prosthetic groups
- BBinds to Cytochrome P450 by strong hydrophobic interactions
- CRequires an iron-sulfur center for activity
- DCan use NADH as readily as NADPH
26Which of the following treatments would increase the likelihood of toxicity resulting from acetaminophen overdose?
- ATaking a drug which increases cytochrome P450 activity
- BTaking an agent which increase glutathione intracellular levels
- CTaking a compound which increases the fluidity of the plasma membrane
- DTaking a compound which inhibits inducible NOS (2) activity
- ETaking a compound that increases renal elimination of sulfate conjugates
27How does the mismatch repair system distinguish between the parental (i.e. correct) DNA strand and the newly synthesized strand containing the mismatched base?
- AThymine in the parental strand of the helix is methylated at GATC
- BThymine in the new strand of the helix is methylated at GATC
- CAdenine in the parental strand of the helix is methylated at GATC
- DAdenine in the new strand of the helix is unmethylated at GATC
28Genes that are “highly expressed” typically possess __________.
- AHypoacetylated histones
- BHyperacetylated histones
- CMethylated cytosines
- DHypoacetylated histones AND methylated cytosines
- EHyperacetylated histones AND methylated cytosines
29Which of the following statements is FALSE?
- AThe steroid-receptor complex interacts with specific regulatory DNA sequences [estrogen response element (ERE)].
- BThe steroid-receptor complex binds to corepressors, thereby initiating transcription of the genes.
- CThe binding of an estradiol to its receptor causes a conformational change in the receptor.
- DThe steroid receptors contain both the ligand-binding and DNA-binding domains.
30_____ is a chemical reaction of purine deoxyribonucleosides, deoxyadenosine and deoxyguanosine, in which the B-N-glycosidic bond is hydrolytically cleaved releasing a free base.
- ADeamination
- BDepurination
- CDNA oxidation
- DUracil DNA glycosylase
31Match the following types of DNA damage to DNA repair system responsible for their repair.
- AO6-alkylguanine DNA alkyltransferase (AGT)
- BMismatch repair (MMR)
- CBase excision repair (BER)
- DNucleotide excision repair (NER)
- EPhotolyase
32Match the following types of DNA damage to DNA repair system responsible for their repair.
- AO6-alkylguanine DNA alkyltransferase (AGT)
- BMismatch repair (MMR)
- CBase excision repair (BER)
- DNucleotide excision repair (NER)
- EPhotolyase
33Which of the following statements are FALSE?
- ADeamination of 5-methyl cytosine creates a G-T mismatch.
- BDeamination of cytosine creates a G-U mismatch.
- CTranscriptionally active regions of DNA have the CpG sequence methylated.
- DDNA cytosine methylation is associated with gene silencing.
34Flavoproteins are usually intermediates in the transfer of electrons from NADPH to cyt P450 because:
- ANADPH cannot enter the membrane.
- BFlavoproteins can accept two electrons from NADPH and donate them one at a time to cytP450.
- CThey have a more negative reduction potential than NADPH so accept electrons more readily.
- DAs proteins, they can bind to cyt P450 while the nonproteins NADPH cannot.
- EThey contain iron-sulfur centers.
35Which of the following statements regarding NADPH-cytochrome P450 reductase is CORRECT?
- AUses both FAD and FMN as prosthetic group.
- BBinds to cytochrome P450 by strong hydrophobic interaction.
- CRequires an iron-sulfur center for activity.
- DCan use NADH as readily as NADPH.
36Benzo[a]pyrene, a xenobiotic produced by combustion of a variety of substances:
- AInduces the synthesis of cytochrome P450.
- BUndergoes epoxidation by a cytochrome P450.
- CIs converted to a potent carcinogen in animals by cytochrome P450.
- DWould be rendered more water-soluble after the action of cytochrome P450.
- EAll of the above
37The DNA double helix structure is STABILIZED by all of the following EXCEPT:
- ASugar-phosphate backbones
- BThe two glycosidic bonds holding the bases are exactly across the helix
- CBoth internal and external hydrogen bonds
- DBases stack together through hydrophobic interactions and van der Waals forces
38The enzymatic activity of HIV reverse transcriptase is best described as:
- ADNA-directed DNA polymerase
- BRNA-directed DNA polymerase
- CRNA polymerase
- DEndonuclease
39All are characteristics of RNA-directed DNA polymerase EXCEPT:
- ASynthesis polynucleotides in the 5’ to 3’ direction
- BAlso called reverse transcriptase
- CFound in retroviruses
- DRNAse H activity
- EAll are true
40A solution contains DNA polymerase I, Mg2+ salts of dATP, dGTP, dCTP, and dTTP, and an appropriate buffer. Which of the following DNA molecules would serve as a template for DNA synthesis when added to this solution?
- AA single-stranded closed circle
- BA single-stranded closed circle base-paired to a shorter linear strand with a 3’-terminal hydroxyl (OH)
- CA single-stranded closed circle base-paired to a shorter linear strand with a 3’-terminal phosphate
- DA double-stranded closed circle
41The PROOFREADING activity of E. coli DNA polymerases:
- AOccur after DNA synthesis is complete
- BIs a function of 5’ 3’ exonuclease activity associated with DNA polymerase itself
- CIs a function of 3’ 5’ exonuclease activity associated with DNA polymerase itself
- DIs a function of 3’ 5’ endonuclease activity associated with DNA polymerase itself
42An Okazaki fragment is a:
- AFragment of DNA resulting from endonuclease action.
- BFragment of RNA that is a subunit of the 30S ribosome.
- CPiece of DNA that is synthesized in the 3’ 5’ direction.
- DSegment of DNA that is an intermediate in the synthesis of the lagging strand.
43The proofreading function of DNA polymerase involves all of the following except:
- A3’ --> 5’ exonuclease
- BBase pairing
- CDetection of mismatched base pairs
- DPhosphodiester bond hydrolysis
- EReversal of the polymerization reaction
44Which of the following statements about DNA polymerase reaction is FALSE?
- AThey add deoxyribonucleotide units to a free 3’-hydroxyl (OH) of a primer
- BAll DNA synthesis require a template DNA
- CThe reaction requires nucleoside triphosphate (dATP, dTTP, dCTP, dGTP)
- DSynthesis polynucleotides in the 3’ to 5’ direction
45The enzyme that seals nicks in the dsDNA where a 3’-OH and 5’-phosphate is:
- ADNA polymerase I
- BDNA topoisomerase
- CDNA polymerase III
- DDNA ligase
46Zidovudine (AZT) is a more effective inhibitor of HIV reverse transcriptase than of mammalian cell DNA polymerases because:
- AAZT crosses the outer mammalian cell membrane more efficiently than it crosses the nuclear membrane.
- BAZT can be converted to a ribonucleotide triphosphate more efficiently than to a dTTP.
- CHIV reverse transcriptase can utilize either an RNA or DNA template, whereas mammalian DNA polymerases can on utilize a DNA template.
- DMammalian DNA polymerases have a 3’ 5’ exonuclease activity, whereas HIV reverse transcriptase does not.
47AZT, the first drug approved use against the human immunodeficiency virus (HIV). Before the drug can inhibit the viral transcriptase, it must be converted to a form of nucleotide by:
- AHGPRT
- BRibonucleotide synthase
- CThymidylate synthase
- DNucleoside phosphorylase
- EThymidine kinase
48Acyclovir was one of the first highly selective antiviral agents for Herpes simplex virus. Which of the following statements about acyclovir are TRUE?
I. Acyclovir is phosphorylated by virus thymidine kinase to form acyclovir monophosphate
II. Acyclovir monophosphate is phosphorylated by cellular kinases to form acyclovir triphosphate
III. Acyclovir triphosphate is a competitive inhibitor for DNA polymerase, incorporated into growing polynucleotide chains in the place of guanosine residues- AI
- BII
- CI, II
- DII, III
- EI, II, III
49One of the functional differences between DNA polymerases and RNA polymerases is that, unlike DNA polymerases, RNA polymerases
- ASupply their own template
- BDo not require a primer
- CDo not require the DNA to be unwound
- DSynthesis nuclei acid with the same polarity as the template, rather than anti-parallel
50The flow of genetic information in Central Dogma of Biology (included the retroviruses) is as follows:
- ARNA --> DNA --> proteins
- BRNA --> DNA --> RNA --> proteins
- CDNA --> RNA --> proteins
- DDNA --> RNA --> DNA --> RNA --> proteins
51Which of the following statements about Pregnane X receptor (PXR) is FALSE?
- AIt is a member of the orphan nuclear receptor family.
- BIt contains ligand-activated binding domain.
- CIt binds as a heterodimer with the 9-cis retinoic acid receptor (RXR) to xenobiotic response elements.
- DIt is highly expressed in the liver and intestine, the same tissues which CYP3A gene expression is induced.
- EIt is activated by CYP3A inhibitors such as pregnenolone 16a-carbonitrile (PCN)
- FPrescription drugs (rifampicin, indinavir and paclitaxel) can activate PXR and stimulate CYP3A expression.
- GThe activated nuclear receptor stimulates the expression of target genes by binding to short DNA sequence motifs, termed xenobiotic response elements in the target genes (CYP3A).
52If a female patient was already taking an oral contraceptive (i.e., birth control pill), what best describes the advice you would provide to her regarding St. John’s wort?
- AShe should take her St. John’s wort one hour before or two hours after taking her oral contraceptive.
- BSt. John’s wort may increase the metabolism of her oral contraceptive.
- CSt. John’s wort may decrease the metabolism of her oral contraceptive.
- DEarly evidence suggested that there may be an interaction between St. John’s wort and oral contraceptives, but the most recent evidence indicates that this is no longer a concern.
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