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COB Molecular > Lec 10. Protein synthesis 3. Translation > Flashcards

Lec 10. Protein synthesis 3. Translation Flashcards

1
Q

Ribosomal RNAs (rRNAs) are transcribed by what?

A

RNA pol I and RNA pol III

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2
Q

What is the size category for rRNA?

A

Mid-range to long

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3
Q

What is the role of rRNA in the cell?

A

Components of the ribosome

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4
Q

True or False? the ribosome is highly conserved

A

True

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5
Q

What are the two parts to the ribosome?

A

Large + small subunits

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6
Q

What is the ribosome composed of?

A

RNA+potein

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7
Q

Is the ribosome a ribozyme?

A

Yes

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8
Q

What are the three binding sites for tRNA?

A

A.P.E

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9
Q

What does the A stand for?

A

Attachment

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10
Q

What does the P stand for?

A

Peptide bond (where peptide bond is forming)

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11
Q

What does the E stand for?

A

Exit

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12
Q

Transfer RNAs tRNAs are transcribed by what?

A

RNA Pol III

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13
Q

What is the size category for tRNAs?

A

Mid-range

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14
Q

What is the role of tRNA in the cell?

A

Deliver amino acids to the growing polypeptide chain

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15
Q

What are some tRNA characteristics?

A

Unique splicing mechanism. Modified nucleotides are abundant. Fewer tRNAs are needed than are codons in the table. Each tRNA has a special tRNA synthetase that adds the appropriate amino acid

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16
Q

Pertaining to tRNA, how modified nucleotides are abundant, what do some of these modification do?

A

Help distinguish tRNA(i)-Met from normal elongating tRNA-met. Since tRNA(i)-Met folds differently

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17
Q

Why are fewer tRNA needed than codons in the table?

A

Wobble position

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18
Q

What is the wobble position?

A

Last position of the codon doesnt have to match perfectly.

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19
Q

What is a substantial source of translational error?

A

Incorporating the incorrect amino acid to a tRNA while undergoing the 2nd proofreading step (clipping off the amino acid if its wrong)

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20
Q

Before starting translation initiation what two things are needed?

A

A 5’ cap and a 3’ poly-A tail

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21
Q

What are the steps to translation initiation?

A
  1. Small subunit binds mRNA first. 2. tRNA(i)-Met binds to the P site. 3.Small subunit+tRNA(i)-Met scans the 5’UTR until it finds AUG. 4. elFs dissociate when large subunit binds. 5.Circularized mRNA facilitates ribosome recycling.
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22
Q

What are 6 important translation initiation factors?

A

elF1, elF2, elF3, elF4F, elF5, elF6

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23
Q

Which of the translation initiation factors is a complex?

A

elF4F

24
Q

What does elF1 do?

A

blocks tRNA(i)-Met from entering A/E sites

25
Q

What does elF2 do?

A

loads tRNA(i)-Met at P site

26
Q

What does elF3 do?

A

loads small subunit onto mRNA, recruits other elFs, promotes scanning, prevents large subunit binding

27
Q

What does elF4F do?

A

binds the mRNA 5’cap

28
Q

What does elF5 do?

A

releases other elFs to allow large subunit binding once AUG found

29
Q

What does elF6 do?

A

Prevents large subunit binding

30
Q

What are the steps to translation elongation?

A
  1. An aa-tRNA enters the A site. 2. The peptide bond forms. 3.The large subunit slides. 4. The small subunit slides down the mRNA, the tRNA is ejected 5. Repeat
31
Q

Pertaining to prokaryotes, what elongation factor recruites aa-tRNA to A site (a G protein)?

A

EF-Tu

32
Q

Pertaining to Eukaryotes, what elongation factor recruites aa-tRNA to A site (a G protein)?

A

eEF1B

33
Q

Pertaining to prokaryotes, what elongation factor regenerates ^(up) (a GEF)?

A

EF-Ts

34
Q

Pertaining to Eukaryotes, what elongation factor regenerates ^(up) (a GEF)?

A

eEF1A

35
Q

Pertaining to prokaryotes, what elongation factor helps ribosome translocation (a g protein)?

A

EF-G

36
Q

Pertaining to Eukaryotes, what elongation factor helps ribosome translocation (a g protein)?

A

eEF2

37
Q

what do G proteins do?

A

hydrolyze GTP

38
Q

What do GEFS do?

A

Regenerate G proteins by swapping the spent GDP from fresh GTP

39
Q

What do GAPS do?

A

Stimulate G proteins to hydrolyze GTP

40
Q

True or False? Translation elongation is highly error prone at fast speeds

A

False. Slow speeds

41
Q

During translation elongation what speeds up the process and increased fidelity?

A

Elongation factors

42
Q

Pertaining to translation termination, eRFs (release factors) are proteins that are shaped like tRNAs but they do not

A

Carry an amino acid for the growing polypeptide chain

43
Q

eRF1 works together with that other release factor?

A

eRF3

44
Q

What does eRF3 do?

A

GTPase (hydorlyze GTP)

45
Q

What does eRF1 do?

A

interacts with stop codon

46
Q

What does NDM stand for?

A

Nonsense mediated decay

47
Q

What do nonsense mutations cause?

A

Premature stop codons

48
Q

What are the two other observations for NMD?

A

10% of all genetic diseases result from nonsense mutations. RNAs containing NMDs are underrepresented in cellular transcriptome

49
Q

What is NMD?

A

is the detection and degradation of mRNAs harboring premature stop codons

50
Q

What important proteins interact with NMD?

A

UPF (up-frameshift) SMG (suppressor of morphogenesis in genetalia) and eRFs

51
Q

What two pathways trigger NMD?

A

Incorrect splicing retains exon junction proteins and 3’ UTR is too long (stop codon came too soon)

52
Q

What is selenocysteine?

A

21st amino acid

53
Q

What does selenocysteine do?

A

Recognizes what is supposed to be a STOP codon AUG

54
Q

What happens when we cant find tRNA selenocysteine?

A

NMD

55
Q

What do chaperone proteins do?

A

Help newly transcribed proteins fold correctly.

56
Q

What are three options when proteins are misfolded?

A

try again: refold in chaperone, Destroy: recycle in proteasome, Escape detection: aggregate and cause disease.

57
Q

How are misfolded proteins degraded?

A

Tagged for degradation in proteasome (polyubiquitinated).

COB Molecular (36 decks)

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