Translation And Regulation

Question 1

What makes up eukaryotic ribosomes

Answer 1

80s ribosome 
40 ss, 60 ls.  
18s rRNA,28s rRNA, 5.8,5 
LS has 50 proteins 
Ss has 33 proteins

Question 2

What is the catalytic subunit of ribosome

Answer 2

Rna

Question 3

What gets transferred to trnas via trna synthetase

Answer 3

Amino acid + adenosine tp (2ppi lost for energy)

= amino adenylate = amino acyl trna

Question 4

Why is ribosomal rna needed

Answer 4

Peptide bond formation is unfavourable

Question 5

What are the 3 sites on the 40s subunit

Answer 5

EPA
Exit
Polypeptide chain site
Amino acyl trna bs

Question 6

What sequence is scanned by the ribosome around the aug start

Answer 6

Kozak consensus

Question 7

Does small subunit 40 bind to cap for initiation

Answer 7

Yes

Question 8

What needs to happen structurally to mrna for initiation

Answer 8

Circularisation by bringing cap and poly a together

Question 9

What complex is responsible for initiation

Answer 9

Eif4 complex (g,e,a)

Question 10

What eif4 binds to the cap

Answer 10

Eif4 E

Question 11

What does eif4 G bind

Answer 11

Eif4 A, 3 and poly A binding proteins and E (circularising mrna)

Question 12

What does eif4 A have

Answer 12

ATPase and rna helicase

Question 13

What is the eif2 complex

Answer 13

Eif2 gtp, attached to trna met (start trna)

Question 14

What does eif2 complex associate with first in translation

Answer 14

43s pic

Recycled 40s subunit, eif 1a,1 and 3

Question 15

Once the 43s is attached to the eif2 trna complex. What attaches

Answer 15

The eif4 E binds to cap, eif4G binds to pabp,3, and E causing circularisation

Question 16

Once the 43s binds with the eif4 complex around the cap, what happens

Answer 16

Can scan the start codon and kozak

Question 17

What happens when start codon is scanned

Answer 17

Eif2 gtp is hydrolysed, the 43s binds with the eif4 complex and eif2complex.
= 48s initiation complex
Trna met can join via anticodon

Question 18

What allows the 60s subunit to bind

Answer 18

Eif5b GTP hydrolysis. This occurs when the 48s initation complex is attached to start codon

Question 19

What happens to eif when 60s binds

Answer 19

All leave at different times

Question 20

What allows elongation by bringing a new amino acyl trna to the A site

Answer 20

Ef G 1a and gtp hydrolysis

Then allows translocation

Question 21

What is peptide forming called

Answer 21

Peptides transferase reaction (via rna catalism )

Question 22

Which release factor binds stop codon in A site

Answer 22

Erf1

Question 23

Which release fsctor cleaves peptide chain from trna

Answer 23

Erf3 gtp hydrolysis

Question 24

after erf3 hydrolysis, what is released and recycled

Answer 24

Ribosomes, trna released

The 40s stays with 1,1a and 3 forming the 43s pic

Question 25

How is EIF2 used to regulate translation

Answer 25

It is phosphorylsted which stops it’s action - means no gtp hydrolysis of eif2 = no start codon recognition and no 48s initation complex

Question 26

When is eif2 inactivated

Answer 26

Eg due to amino acid shortage or cell stress

Question 27

What dephosphorylates eif2 activating it

Answer 27

Growth factors

Question 28

How can eif2 regulation be used to switch only mrna to do with stress eg heat shock on for translation

Answer 28

Via distinctive elements on mrna which identifies them

Question 29

How does level of irons impact

Answer 29

They regulate expression of transporters of iron or storage of iron if too high

Question 30

What are UTRs

Answer 30

Untranslated regions on mrna 5’ Utr Is between cap and start codon (binding blocks ribosome scanning) 3’ is between stop codon and poly A (for stability)

Question 31

What happens in low iron levels

Answer 31

Mrna for transporters is up regulated to get more iron This is via IRP1 binding to the 3’ utr for stability = more expression IRP1 binds to 5’ utr on storage mrna = blocked translation

Question 32

What does IRP1 bind to on rnas

Answer 32

IREs

Question 33

In high iron levels, the iron binds to IRP1, how does this have effect on storage mrna

Answer 33

It means IRP1 can’t block translation of storage mrna because can’t bind to 5’ utr = translated Also means it can’t stabilise at 3’ utr for the transporter mrna = unstable and degraded

Question 34

What does bi functionality of IRP1 mean

Answer 34

When it’s bound to iron it changes it’s role to a c aconitase