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PHA 411 > Nucleic Acid Synthesis Inhibitors > Flashcards

Nucleic Acid Synthesis Inhibitors Flashcards

1
Q

Nuclear bases + sugar = __________ + phosphate = __________ = ________

A

Nucleoside, nucleotide, nucleic acid

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2
Q

DNA replication begins when polymerase enzyme
unwinds and separates the bonds between the two
DNA strands. T or F

A

False. DNA replication begins when helicase enzyme
unwinds and separates the bonds between the two
DNA strands

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3
Q

DNA polymerases enzymes make use of a primer to make new DNA by adding nucleotides to a 3’ hydroxyl group on the
primer. T or F

A

True

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4
Q

When nucleotides are added to the 3’ end of the primer or the new DNA strand, a bond is formed between the 3’ phosphate group of the primer/new
DNA and the 5’ hydroxyl group of the nucleotide. T or F

A

False. When nucleotides are added to the 3’ end of the
primer or the new DNA strand, a bond is formed
between the 3’ hydroxyl group of the primer/new
DNA and the 5’ phosphate group of the nucleotide.

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5
Q

What are the 3 classes of nucleic acid inhibitors?

A

DNA inhibitors

RNA inhibitors

Antifolates (DNA, RNA, Proteins)

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6
Q

Give an example of a first generation quinolone

A

Nalidixic acid

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6
Q

What is the MOA of quinolones?

A

The quinolones inhibit DNA replication during cell division by blocking the action of DNA
gyrase (topoisomerase II), an enzyme responsible for simultaneous unwinding of both strands of DNA during
replication process.

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6
Q

What classes of antibiotics fall under DNA inhibitors?

A

Quinolones, Nitrofurantoin, Nitroimidazoles

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6
Q

Which topoisomerase inhibitors are used as antineoplastic drugs to kill cancer cells?

A

irinotecan and
etoposide

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6
Q

Give 6 examples of second generation quinolones (fluoroquinolones)

A

ciprofloxacin, enoxacin,
gatifloxacin, grepafloxacin,
levofloxacin, lomefloxacin,
moxifloxacin, norfloxacin,
ofloxacin, sparfloxacin, and
trovafloxacin

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7
Q

Quinolones are specific inhibitors
of bacterial topoisomerase II. T or F

A

True

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7
Q

______ and ______ are inhibitors that are effective
against mammalian topoisomerases

A

irinotecan and
etoposide

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8
Q

Quinolones inhibit the B subunit of DNA gyrase. T or F

A

False. Quinolones inhibit the A subunit of DNA gyrase

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9
Q

Quinolones are bacteriostatic. T or F

A

False. The quinolones rapidly inhibits DNA synthesis
and are bactericidal unless growth is prevented

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10
Q

What can nalidixic acid be used to treat?

A

Urinary tract infections

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11
Q

Nalidixic acid is too toxic for systemic use. T or F

A

True

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12
Q

________ is indicated for the oral treatment of
urinary tract infections, uncomplicated gonococcal
infections, and prostatitis.

A

Norfloxacin

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13
Q

_________ is approved for use in urinary tract
infections; lower respiratory infections; sinusitis; bone,
joint and skin structure infections; typhoid fever;
urethral and cervical gonococcal infections; and
infectious diarrhea

A

Ciprofloxacin

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14
Q

Which antibiotic causes cartilage toxicity and joint swelling in children

A

Quinolones

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15
Q

Which antibiotic causes Pseudomembranous Colitis due to overgrowth
of Clostridium difficile.

A

Quinolones

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16
Q

Which antibiotic causes Worsening of
myasthenia gravis

A

Quinolones

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17
Q

Which antibiotic causes Increased risk of tendonitis & tendon rupture

A

Quinolones

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18
Q

Give examples of antibiotics that fall under the class nitroimidazole

A

Benznidazole, metronidazole, nimorazole, ornidazole,
secnidazole, satranidazole, tinidazole,

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18
Q

State the mechanism of action of nitroimidazoles

A

They generate metabolites that are
incorporated into DNA strands rendering them more prone to
breakage.

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19
Q

Nitroimidazoles are selectively toxic to aerobic organisms,
and can’t affect human cells. T or F

A

False. These drugs are selectively toxic to anaerobic organisms,
but can affect human cells.

20
Q

What are nitroimidazoles used to treat?

A

They are used for amoebiasis, trichomoniasis,
bacteria vaginosis, giardiasis and obligate anaerobic bacteria
infections

21
Q

Which class of antibiotic leaves a metallic taste and prolonged administration may
cause peripheral neuropathy and seizures

A

Nitroimidazole

22
Q

Nitrofurantoin is activated inside bacteria
by reduction via the ____ to
unstable metabolites, which disrupt ribosomal RNA, DNA and
other intracellular components.

A

flavoprotein nitrofurantoin reductase

23
Q

Nitrofurantoin is used to treat urinary tract
infections. T or F

A

True

24
Q

Which antibiotic causes numbness and pain in your hands and feet?

A

Nitrofurantoin

25
Q

Mutations in enzymes may cause quinolone resistance. T or F

A

True

26
Q

Mutation of serine or acidic residue decreases the affinity
of drug and enzyme complex. T or F

A

True

27
Q

Disruption of the metal ion bridge may
also cause nitroimidazole resistance. T or F

A

False. Disruption of the metal ion bridge may
also cause quinolone resistance.

28
Q

Mutations at ______ decrease
catalytic activity while _______ in gyrase and topoisomerase IV does
not affect catalytic activity.

A

acidic residue, serine residue

29
Q

Qnr genes that encode ____, ______ and _____ decrease the binding of enzymes to DNA.

A

proteins
and McbG and MfpA

30
Q

Thus,
quinolones were protected and these genes (QNR) bind to _____ and _____ and inhibit quinolones from entering into complexes.

A

gyrase and
topoisomerase

31
Q

_____ facilitates drug
efflux which leads to resistance

A

Expression of porins

32
Q

State the mechanisms of resistance to DNA inhibitors.

A
  1. Mutations in enzymes
  2. Plasmid-mediated quinolone resistance
  3. Chromosome mediated quinolone resistance
33
Q

Give 3 examples of RNA synthesis inhibitors

A

Rifampicin, doxorubicin, actinomycin D

33
Q

State the mechanism of action of Rifampicin

A

Rifampicin blocks initiation of RNA synthesis by specifically inhibiting bacterial RNA polymerase.

34
Q

Rifampicin is specific for
Gram-positive bacteria and some Gram-negative bacteria. T or F

A

True

34
Q

Rifampicin does not
interact with mammalian RNA polymerases. T or F

A

True

35
Q

Which RNA synthesis inhibitors are used for cancer treatment?

A

Doxorubicin
and dactinomycin

35
Q

Rifampicin, Doxorubicin and actinomycin D (dactinomycin) interfere with both
bacterial and mammalian RNA Polymerase. T or F

A

False. Only doxorubicin and actinomycin D (dactinomycin) interfere with both
bacterial and mammalian RNA Polymerase.

36
Q

Which RNA synthesis inhibitor causes temporary discolouration of skin and difficulty concentrating?

A

Rifampicin

37
Q

Which RNA synthesis inhibitor causes cough or hoarseness accompanied by fever or chills and fast or irregular heartbeat?

A

Doxorubicin

38
Q

Which RNA synthesis inhibitor causes hair loss, abdominal swelling and swallowing difficulty?

A

Dactinomycin

39
Q

Which antifolates are antibacterials?

A

Sulphonamides, trimethoprim, proguanil
and pyrimethamine

40
Q

Which antifolates are anticancer?

A

methotrexate, pemetrexed

41
Q

What is the mechanism of action of antifolates?

A

Antifolates indirectly inhibit RNA and DNA
synthesis by antagonizing the action of folic acid (vitamin B9) which is
a cofactor to various methyltransferases involved in serine,
methionine, thymidine and purine biosynthesis, which in turn are
required for cell division, DNA/RNA synthesis and repair and protein
synthesis.

42
Q

Proguanil, pyrimethamine and trimethoprim selectively
inhibit folate’s actions in microbial organisms such as bacteria,
protozoa and fungi by inhibiting ______

A

dihydrofolate reductase

43
Q

Methotrexate and
pemetrexed inhibit _____

A

dihydrofolate reductase

43
Q

Sulphonamides inhibit ______

A

dihydropteroate synthetase

44
Q

_______ for
treatment and prophylaxis for Pneumocystis jirovecii pneumonia

A

Trimethoprim combined with sulfamethoxazole (co-trimoxazole)

45
Q

Proguanil (_______, _______) and pyrimethamine (_____,
______) are for malaria prophylaxis.

A

Paludrine, Reludrine, daraprim, metaprim

46
Q

Pyrimethamine sometimes
combined with sulphadoxine (fansidar, swidar, amalar, maldox) for?

A

Malaria prophylaxis

47
Q

Methotrexate and permetrexed
are used as anticancer agents. What else are they used for?

A

Methotrexate: (osteosarcoma, rheumatoid arthritis)

Permetrexed: (lung carcinoma)

48
Q

Most antifolates are associated with what side effects?

A

Steven-Johnson
syndrome, toxic epidermal necrolysis, agranulocytosis and
aplastic anaemia

49
Q

The use of _______ is strongly contraindicated in pregnancy and
carries significant teratogenic risk

A

co-trimoxazole

50
Q

The long-term effectiveness of antifolates is diminished by cellular
response. T or F

A

True

51
Q

Because methotrexate is a competitive inhibitor of DHF
reductase, _______ can overcome
the drugs inhibition

A

increased concentrations of DHF reductase

PHA 411 (3 decks)

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