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STEP1 > Step1_BioChem > Flashcards

Step1_BioChem Flashcards

1
Q

[ssDNA Repair] Nucleotiide exision repair

A

specific endonucleases release the oligonucleotinde -containing damaged bases; DNA polymerase and ligase fill and reseal the gap (respectively)–> Repair BULKY helix distorign lesions

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2
Q

[ssDNA Repair] Nucleotiide exision repair - Clinical relevence

A

Mutated in Xeroderma Pigmentosum - which prevents repair of pyrimidine dimers because of UV light exposure

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3
Q

[ssDNA Repair] Base excision repair

A

Specific glycolases recognize and remove damaged bases, apurinic/apyrimidinic endonucleases cut DNA at both apurininc and apyrimidinic sites - empty sugar remoed – gap filled and resealed

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4
Q

[ssDNA Repair] Base excision repair - Clinical relevance

A

Repair of spontaneous/toxic deamination

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5
Q

[ssDNA Repair] Mismatch repair

A

Newly synthesized strand - recognized - mismatched nucleotides are removed - gap filled and resealed

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6
Q

[ssDNA Repair] Mismatch repair - Clinical relevance

A

Mutated in HNPCC

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7
Q

[dsDNA Repair] Nonhomologus end joining

A

Brings together 2 ends of DNA fragments to repair ds breaks. No requirment for homology

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8
Q

[dsDNA Repair] Nonhomologus end joining

A

Mutatedin ataxia telangiectasia

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9
Q

rRNA

A

most abundant

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10
Q

mRNA

A

longest

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11
Q

tRNA

A

smallest; CCA at the3’ end; anticodon end is opposite the aminoacyl end

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12
Q

aminoacyl-tRNA

A

synthase and binding of charged tRNA to codon –> responsible for accuracy of amino acid selection

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13
Q

Tetracyclines

A

bind 30S subunit –> prevent attachement of aminoacyl-tRNA

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14
Q

mRNA Start Codons

A

AUG (rarely GUG)

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15
Q

[mRNA start codon] Eukaryotes

A

Codes for methionine

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16
Q

[mRNA start codon] Prokaryotes

A

Code for formmymethionine (f-met)

17
Q

mRNA Stop Codons

A

UGA, UAA, UAG

18
Q

[Eukaryotes] RNA polymerase I

A

makes rRNA

19
Q

[Eukaryotes] RNA polymerase II

A

makes mRNA; opens DNA at polymerase site; inhibted by alpha-amanitin (death mushroom)

20
Q

[Eukaryotes] RNA polymerase III

A

makes tRNA

21
Q

alpha-amanitin [Amanita phallodes - death cap mushroom]

A

inhibits RNA polymerase II –> severe HEPATOTOXICITY

22
Q

tRNA Wobble

A

accurate base pairing only required in the first 2 nucleotide positions of an mRNA codon - may differ in the 3rd “wobble” posistion – code for the same tRNA/amino acid (2/2 degeneracy of genetic code)

23
Q

[Protein Synthesis] Initiation

A

Activated by GTP hydrolysis; initiation factors help assemble 40S ribosomal subunit w/initiator tRNA –> released when mRNA and ribosomal subunit assemble with the complex

24
Q

[Protein Synthesis] Elongation

A

(1) Aminoacyle -tRNA binds to A site (except for initiator methionine); (2) Ribosomal rRNA (“ribozyme”) - catalyze peptide bond formation –> transfer growing polypeptide to amino acid in A site; (3) Ribososome advances 3 nucleotide toward 3’ end of mRNA, moving peptidyl tRNA to P site (translocation)

25
Q

[Protein Synthesis] Termination

A

Stop codon is recognized by release factor –> complete protein released frm the ribosome

26
Q

[Abx - Protein synthesis inhibitors] Aminoglycosides

A

bind 30S and inhibit formation of initation complex and cause misreading of mRNA

27
Q

[Abx - Protein synthesis inhibitors] Tetracyclines

A

bind 30S and block aminoacyl tRNA from entering the acceptor site

28
Q

[Abx - Protein synthesis inhibitors] Chloramphenicol

A

binds 50S and inhibits petidyl transferase

29
Q

[Abx - Protein synthesis inhibitors] Macrolides

A

binds 50S and prevent release of uncharged tRNA after it has donated its amino acid

30
Q

[posttranslational modification] Trimming

A

Removal of N or C-terminal propeptides from zymogens to generate mature proteins

31
Q

[posttranslational modification] Covalent alterations

A

P”, glycosylation, hydroxylation, methylation, and acetylation

32
Q

[posttranslational modification] Proteasomal degradation

A

attachment or ubiquitin to defective prteins to tag them for breakdown

33
Q

Drugs that act on Microtubules

A

Mebendazole/thiabendazole (antihelmenthic); Griseofulvin (antifungal); Vincristinevinblastine (anti-cancer); paclitazel (anti-brest cancer); cholchicine (anti-gout)

34
Q

Chediak-Higashi Syndrome - pathophys

A

mutation in lysosomal trafficking regulator gene (LYST) - product required for micotuble-dependent sorting of endosomal proteins into late multivesicular endosome

35
Q

Chediak-Higashi Syndrome - clinical

A

recurrent pyogenic infections, partial albinism, periferal neuropathy

STEP1 (13 decks)

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