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Biology - Genetics > Biochemistry PS - Translation > Flashcards

Biochemistry PS - Translation Flashcards

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1
Q

What allows tRNAmet to bind?

A

Recruitment of eIF4F to the 5’ cap then eIF4A and eIF4B

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2
Q

What do eIF4F, A and B function to do?

A

Create a binding site for tRNAmet-eIF2, and the 40S ribosomal subunit

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3
Q

What happens after eIF4F recruitment?

A

3’direction scanning of mRNA until AUG is recognised.

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4
Q

Why is the AUG codon signification?

A

It marks the methionine amino acid for synthesis.

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5
Q

What happens when AUG is recognised?

A

eIF5 release alls initaition factors and 60S subunit is recruited.

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6
Q

What are the three binding sites of the 60S subunit(right to left)?

A

Exit, Peptidyl and Aminoacyl

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7
Q

What does the tRNA-met do in initation?

A

It is in the P site, whilst either side are empty

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8
Q

How does tRNA associate to the mRNA?

A

tRNA anticodon arm hydrogen bonds for AUG codon bases.

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9
Q

Monocistronic

A

This means only one gene is produced from a promoter region of a stretch of replication DNA

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10
Q

What is eukaryotic mRNA in regards to their expression capabilities?

A

Monocistronic

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11
Q

When is elongation marked as starting?

A

EF-1A-GTP recruited into initation complex.

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12
Q

How is movement of the ribosomal subunits mediated?

A

EF-1a/EF2 hydrolysis of their associated GTP into GDP.

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13
Q

What happens when EF-1a-GTP is first hydrolysed?

A

40S subunit moves one down, new charged tRNA recruited at A site of 60s, where new EF-1a-gtp is found.

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14
Q

What is required for EF-1a-GTP hydrolysis?

A

codon-anticodon resemblence

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15
Q

What happens when EF-1a-GTP hydrolysis occurs secondly?

A

CC clamps charged tRNA allowing peptidyl transferase to catalyse peptide bond formation.

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16
Q

What is peptide bond formation coupled with?

A

Breakage of bond connecting amino acid to tRNA.

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17
Q

What happens after the peptide bonds are formed?

A

60s moves along, tRNA in the P and A shift to E and P.

18
Q

How quick is tranlastion elongation?

A

15 amino acids per second.

19
Q

What happens when the termination codon is encounted?

A

Release factor binds ribosome, cleaving remaining tRNA from PP chain by GTP hydrolyis.s

20
Q

What are the stop codons?

A

UAA, UAG and UGA

21
Q

What are the two types of regulation mechanisms?

A

Prevention of incorporation of errors and termination of PP synthesis when an error is incorporated.

22
Q

What an example of prevention of error?

A

Regualtory proteins binding introns, removed just prior to translation assuming not bound to introns

23
Q

Why are introns potentially bad for mRNA?

A

Because they are long enough to usuually contain a stop codon spontaneously.

24
Q

What happens if an intron gets through?

A

Protein markers remain before being stripped away, inducing nuclease destruction of the mRNA

25
Q

Nonsense-mediated decay

A

This prevents translation of mutant mRNA harbouring premature termination codons by targeting them for degradation.

26
Q

What may assist protein folding?

A

Nascent Chain Associated Complex or chaperones like HSP40/70/90 or chaperonins?

27
Q

What do chaperones do?

A

Bind hydrophobic regions to prevent aggregation, allowing time for folding.

28
Q

What do chaperonins do?

A

Cylindrical structures providing safe-envrionment for folding to occur.

29
Q

What mediates translation of mRNA to amino acid sequence?

A

Charged tRNA molecules, ie aminoacyl-tRNA synthestase

30
Q

Structure of mRNA in 2D?

A

Four0clover leaf, containing an anticodon opposing the amino acid attachment site and a D loop opposing the T loop

31
Q

Importance of the anticodon loop?

A

Base pairs with mRNA sequence

32
Q

Amino acid attachment site…

A

A 3; 0H group terminated by a CCA end where amino acid is attached by aminoacyl tRNA synthetase

33
Q

What happens when synthetase binds tRNA attachment site?

A

Part of protein contacts T loop guiding the acceptor arom into enzymes active site

34
Q

D Arm

A

Recognition site for aminoacyl-tRNA synthetase

35
Q

T Arm

A

Recognition site for the ribosome to form a tRNA ribosome complex

36
Q

Function of eIF5?

A

Interacts with 40s iniation complex to promote GTP hydrolysis joining 60S subunit to 40S initaiton complex

37
Q

43S pre-initation complex

A

A ribonucleoprotein in early translation containg the EIFs

38
Q

First step of intiation

A

AUG start codon is in the P site of the ribosome with a met-tRNA naticodon base pair ON the mRNA

39
Q

Second step of initaiton

A

43S PIC contaiing met-tRNA and many EIF recruited to 5’ cap of the mRNA

40
Q

Third step of initation

A

The PIC scans mRNA for complementary codon where GTP-eIF2 anchors PIC to mRNA

41
Q

What happens after GTP-eIF2 hydrolyss?

A

eIF2-GDP is released, forming the 60S subunitm with aminoacyl site ready for new tRNA

42
Q

EF-1a

A

Delivers charged tRNA to ribosome in translation.

Biology - Genetics (14 decks)

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