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Flow Of Genetic Information > Protein Translation > Flashcards

Protein Translation Flashcards

1
Q

How much ATP does it cost to add an amino acid to a polypeptide?

A

4xATP

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2
Q

What is the ribosomes general structure?

A

Made of 2 subunits (small and large), their association creates three sites E,P andA and a tunnel through small subunit for the mRNA. In small subunit.

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3
Q

What is the ORF?

A

Open reading frame

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4
Q

How is the ORF decided?

A

By the template as it decides where you start so what frame its in.

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5
Q

What are the 3 steps of protein translation?

A

Initiation
Elongation
Termination

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6
Q

What is the rate limiting step in protein synthesis?

A

Initiation as it is the slowest step

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7
Q

How is protein translation initiated?

A

The mRNA small ribosomal subunit and first tRNA at initiation codon. Then the large subunit joins.

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8
Q

How is protein elongation done?

A

Correct AA ensured by mRNA to tRNA complementary. Then the amino acid is join by the peptidyl transferase. Shifts along once all 3 sites are full expels first tRNA.

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9
Q

How does termination of protein translation occur?

A

When stop codon is reached there aren’t any complementary AA. So release factors bind and cause it to separates.

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10
Q

What happens to ribosome subunits after protein translation?

A

Ribosomal subunits are recycled and kept separate for next round of translation.

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11
Q

What is needed for bacterial protein synthesis initiation?

A

Formylmethione-tRNA +30s subunit

Also have IF1 IF2 IF3

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12
Q

How is the start codon lined up in prokaryote protein synthesis?

A

mRNA contains shine-Delgarno sequence that binds 3’. End of 16s subunit rRNA. This place start codon in the p-site of ribosome.

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13
Q

Once shine-delgarno sequence is bound what happens in prokaryote protein synthesis?

A

50s subunit associates releasing IF1 and IF3. GTP is hydrolysed causing IF2 to dissociate. This gives you a 70s ribosome with first tRNA in the P-site.

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14
Q

How is the pre initiation complex in eukaryotic protein translation formed?

A

eIF4G bind to the poly A tail via a poly A binding protein and then to the MG7 cap via eIF4E creating a circular mRNA. eIF3 binds to 4G and to 40s subunit to hold it together.

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15
Q

How do proteins fold?

A

Some fold spontaneously yet other require chaperones to help them fold

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16
Q

What is the point of PERK?

A

It exists to couple protein synthesis to folding

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17
Q

How is PERK protein controlled?

A

Bind to BIP to keep it inactive in monomeric state. BIP dissociates to bind unfolded protein allowing PERK to dimerise and sort out folding of proteins.

18
Q

What is the Walcott-Rallison disease?

A

Loss of perk function- causes type 1 diabetes,growth retardation and other things as well.

19
Q

How many codon combinations are there?

A

64 to code for 20 amino acids

20
Q

What is the structure of tRNA?

A

Th contain 70-90 bases with internal pairing. The 3’ terminus has the code CCA the last Adenine Hayes it OH group to bind to each AA via an ester bond.

21
Q

Where does the input energy for peptide bond come from?

A

The hydrolysis of the ester bond holding the amino acid to the tRNA helps drive the synthesis of the peptide bond.

22
Q

How is it ensured that amino acids are attached to the right tRNA?

A

High specific enzymes are used aminoacyl-tRNA-sythetases

23
Q

How do amino-acyl tRNA synthetases work?

A

They bind and recognise the tRNA and the AA. Then catalyse a reaction between the terminal adenine and the AA carboxyl group forming an ester bond

24
Q

What is the mechanism of amino acid activation?

A

1) amino acid+enzyme+ATP —} enzyme AMP-amino acid+ PPi

2) Enzyme AMP-amino acid+ tRNA—-} AMP+enzyme+ Aminoacyl tRNA

25
Q

How much ATP does it cost to produce one aminoacyl tRNA?

A

2 ATP

26
Q

How does proof reading of tRNA production occur?

A

Aminoacyl-tRNA synthetases have an acylation and hydrolytic active site. If a larger AA can’t enter acylation site. If smaller enters acylation site joins tRNA but is small enough to then enter the hydrolytic site so is removed from tRNA.

27
Q

Where are ribosome subunits assembled?

A

In the nucleolus

28
Q

Bacterial 70s ribosomes are made of what subunits?

A

50s and 30s

29
Q

Eukaryotic 80s ribosome is made of what subunits?

A

60s and 40s

30
Q

Key features of 30s subunit?

A

Contain decoding centre
Helix 44 of 16s rRNA is A+P binding sites
3’ of 16s rRNA compliments shine delgarno sequence

31
Q

Key features of 50s subunit?

A

Contains peptidyl transferase centre (PTC) and also the peptide exit tunnel.

32
Q

What domain of the 50s subunit is the peptidyl transferase?

A

Domain V

33
Q

What enzyme is used to join amino acids?

A

Peptidyl transferase

34
Q

What is a ribozyme?

A

RNA. Molecule capable of acting as an enzyme.

35
Q

What are the sites of a ribosome?

A

A,P,E

36
Q

What do you find in each ribosome site?

A

A- aminoacyl tRNA
P- peptidyl tRNA
E-deacetylated tRNA so exits

37
Q

Where is the peptide bond formed?

A

P-site

38
Q

How does the peptide bond form?

A

Nucleophillic attack by incoming amino group. Ribosome works by positioning substrates and water to aid proton transfer and stabilise intermediates. Ribosome doesn’t do catalysis instead reduces activation energy for bond formation

39
Q

What do elongation factors do?

A

Elongation factors check fidelity of codon and anticodon pairing

40
Q

Elongation in bacteria:

A

Next amino acylation tRNA (AAT) binds to A site aided by EFTu-GTP of complementary codes hydrolysed to EFTu-GDP which release the AAT peptide bond formation then occurs. Moves to P-site then spent AAT moved out of the E-site.

Flow Of Genetic Information (4 decks)

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