lecture 9 recap

Question 1

prokaryotic ribosome is

Answer 1

70S (large subunit is 50S and small subunit is 30S)

Question 2

eukaryotic ribosome is

Answer 2

80S (large subunit is 60S and small subunit is 40S)

Question 3

tRNA first binds to the A site which is the

Answer 3

aminoacylated tRNA binding site

Question 4

every thing shifts due to the

Answer 4

elongation factor

Question 5

the peptide chain is passed to the new tRNA with the new amino acid on to which site

Answer 5

P site (polypeptide chain site)

Question 6

the old tRNA move to which site

Answer 6

E site (exit site)

Question 7

where does the small subunit of the ribosome bind

Answer 7

to the cap

Question 8

the small subunit then scans the mRNA till it finds the

Answer 8

AUG then translation starts

Question 9

sequence in front of the AUG is the

Answer 9

kozak consensus - CC(A/G)CC
it improves translation initiation

Question 10

when does the large subunit join

Answer 10

when the small subunit has found the start codon

Question 11

eIF4F complex comes in which contains

Answer 11

eIF4E, G and A

Question 12

eIF4F complex comes in and binds to what

Answer 12

the cap

Question 13

the poly A tail is bound by what

Answer 13

PABP (poly A binding protein)

Question 14

the PABP comes round and binds to the

Answer 14

eIF4F

Question 15

this makes the mRNA

Answer 15

circularised - helps the ribosome come back to the cap

Question 16

which part of eIF4F links to the PABP

Answer 16

eIF4G

Question 17

what does eIF4A do

Answer 17

its an ATPase and RNA helicase which opens up the structure before the AUG to allow the small subunit to scan along without blockage

Question 18

small subunit is bound to what

Answer 18

eIF2

Question 19

eIF2 is a

Answer 19

GTPase which forms the PIC with tRNA

Question 20

when the AUG is recognised the GTP of eIF2 is

Answer 20

hydrolysed released phosphate

Question 21

eIF2 then leaves and the 60S subunit comes in with

Answer 21

eIF5B (also a GTPase)

Question 22

eIF5B GTP is hydrolysed and eI5FB is

Answer 22

released

Question 23

next tRNA comes in with what

Answer 23

eEF1A which is coupled with GTP and tRNA docks in the A site

Question 24

then there is peptide bond formation between the

Answer 24

2 amino acids

Question 25

eEF2 comes along and helps what

Answer 25

translocation of the mRNA allowing the next tRNA to come in

Question 26

termination:
when ribosome gets to stop codon what comes in and sits in the A sit

Answer 26

eRF1

Question 27

the peptide is released from the tRNA and the 2 ribosome subunits are

Answer 27

pulled apart

Question 28

low iron:
dont need storage proteins so theyre repressed
what binds to the region in 5 UTR leading to translational repression

Answer 28

IRP 1/2

Question 29

transport proteins are upregulated IRP 1/2 binds to 3’ UTR causing what

Answer 29

mRNA stabilisation

Question 30

irp =

Answer 30

iron responsive proteins

Question 31

high iron:
iron binds to the IPR1 and IPR2 is

Answer 31

degraded
no binding to 5 or 3 UTR