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Med 103 > translation > Flashcards

translation Flashcards

1
Q

what is the central dogma

A

transcription and translation

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2
Q

what is a codon

A

A series of three adjacent bases in an mRNA molecule codes for a specific amino acid

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3
Q

what three codes dont specify amino acids

A

stop codons, UAA, UAG, and UGA

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4
Q

what is the function of tRNA

A

molecular “bridges” that connect mRNA codons to the amino acids they encode

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5
Q

what is wobble pairing

A

when atypical base pairs—between nucleotides other than A-U and GC—can form at the third position of the codon

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6
Q

what is the rule of wobble pairing

A

G anticodon can pair with C or U but not at A or T in the third position

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7
Q

what is the process of covalently attaching an amino acid to the tRNA

A

Charging

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8
Q

what enzyme attaches the appropriate amino acid onto its tRNA

A

An aminoacyl-tRNA synthetase (aaRS or ARS), also called tRNA-ligase

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9
Q

what are the slots on ribosomes where tRNAs find their matching codons on mRNA

A

A (aminoacyl), P (peptidyl), and E (exit) sites

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10
Q

what is the most common initiator amino acid

A

methionine

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11
Q

during initiation of translation in bacteria, what initiation factors bind to the 30S ribosomal subunit

A

IF1,2,3 with 2 specifically recognizing the initiator tRNA

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12
Q

what does the ribosomal complex recognize when binding to the 5’ end of the mRNA

A

5’ cap

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13
Q

what direction does the complex “walk” along the mRNA

A

in the 3’ direction

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14
Q

what happens when IF3 is released from the complex

A

50S ribosomal subunit associate with the complex

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15
Q

what does the 50S binding trigger

A

hydrolysis of GTP bound to IF2

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16
Q

what happens after hydrolysis of GTP in bacterial translation

A

IF1 and IF2 are released

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17
Q

in bacteria, what brings the second tRNA to the A site

A

EF-Tu which then leaves the ribosome following GTP hydrolysis

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18
Q

what pulls the mRNA onwards by one codon

A

EF-G

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19
Q

what is required in order for translocation to continue in bacteria

A

active EF-Tu/GTP complex regenerated by EF-Ts

20
Q

what proteins recognize stop codons during termination

A

release factors

21
Q

what does the release factor cause addition of instead of an amino acid

A

a water molecule

22
Q

what doe
a) RF1
b) RF2
in prokaryotic cells recognize

A

a) UAA or UAG

b) UAA or UGA

23
Q

in eukaryotic cells the release factor recognizes two termination codons. true or false

A

false, it recognizes all three

24
Q

what is the function of RF3

A

doesn’t recognize specific termination codons but act together with the other RFs

25
Q

what is a polysome

A

A number of ribosomes can translate a single mRNA simultaneously, forming a polyribosome

26
Q

what is an advantage of a polyribosome

A

enable a cell to make many copies of a polypeptide very quickly

27
Q

what are the five mechanisms of regulation of translation

A 
•binding of repressor proteins 
•repressors binding to regulatory sequences and initiation factor of 3’untranslated region and 5’ cap
•mRNA localization 
•modulation of IF activity 
•small regulatory RNA 
(go read page 42 to 52)
28
Q

how many more initiation factors do eukaryotes have then prokaryotes

A

6 more

29
Q

what is scanning in eukaryotic cells

A

40S ribosomal subunit attaches at the 5’ end of the mRNA and moves downstream (i.e. in a 5’ to 3’ direction) until it finds the AUG initiation codon

30
Q

what is the function of tetracycline

A

Blocks attachment of the aa-tRNA to the A site in the ribosome

31
Q

what is the function of erythromycin

A

Blocks the movement of the ribosome down the mRNA

32
Q

what is the function of streptomycin

A

Blocks formation of the initiation complex and causes miscoding

33
Q

what is the function of rifamycin

A

Blocks transcription by blocking binding of RNA polymerase

34
Q

why shouldn’t we antibiotics randomly

A
  • prevent resistance

* avoid killing beneficial bacteria

35
Q

what helps polypeptide chain coil and fold into 3D shape

A

chaperon proteins

36
Q

what are the three ways of protein processing

A
  • Protein Cleavage
  • Glycosylation
  • Attachment of Lipids
37
Q

what does protein cleavage include

A

Removal of the initiator methionine from the amino terminus

38
Q

what are the functions of glycoproteins

A

(1) in protein folding in the ER
(2) targeting of proteins for delivery to the appropriate intracellular compartments
(3) recognition sites in cell-cell interactions

39
Q

what are the three general types of lipid additions on proteins

A

Nmyristoylation, prenylation, palmitoylation

40
Q

what are the two major protein degradation pathways

A
  • the ubiquitin-proteasome pathway

* lysosomal proteolysis

41
Q

what is a polypeptide that is highly conserved in all eukaryotes

A

Ubiquitin

42
Q

what degrades the polyubiquinated proteins in the UPP

A

proteasome

43
Q

what does the lysosomal proteolysis pathway involve formation of

A

formation of vesicles (autophagosomes) contain proteins derived from the ER

44
Q

what do the autophagosomes fuse with in the lysosomal proteolysis pathway

A

Lysosomes

45
Q

what chaperones are required for lysosomal degradation

A

A member of the Hsp70 family of molecular chaperones

46
Q

what proteins are susceptible to degradation the lysosomal proteolysis pathway

A

long-lived but dispensable proteins (usually during starvation)

47
Q

what are the amino acids sequence of proteins degraded by lysosomal proteolysis pathway similar to

A

broad consensus sequence Lys-Phe-Glu-Arg-Gln,

Med 103 (13 decks)

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