Translation

Question 1

2 subunits in bacterial translation

Answer 1

30S and 50S to make 70S (note not additive)

Question 2

2 subunits in euk translation

Answer 2

40S and 60S to make 80S (not not additive)

Question 3

3 tRNA binding site

Answer 3

A P and E

Question 4

small subunit contains what

Answer 4

decoding groove where mRNA passes and tRNAs read the message

Question 5

large subunit contains what

Answer 5

catalytic center (peptidyl transferase center aka PTC which is made entirely of RNA)

Question 6

how many possible codon combos are there

Answer 6

4^3=64

Question 7

what part of the tRNA binds to the codons

Answer 7

anticodon loop

Question 8

what is an aminoacyl tRNA synthetase

Answer 8

protein enzyme that ID’s the right tRNA and puts the correct amino acid on there

Question 9

how many initiation factors are in bacteria and how many in euks

Answer 9

3 in bacteria, >12 in euks

Question 10

what do initiation factors do

Answer 10

bring ribosome to the mRNA and help get it assembled

Question 11

what do elongation factors do

Answer 11

deliver tRNAs and move the ribosome down the message

Question 12

what do release factors do

Answer 12

end the process of translation at a stop codon and help disassociate the subunits

Question 13

start codon?

Answer 13

AUG for methionine

Question 14

3 stop codons

Answer 14

UAA UAG UGA

Question 15

define degeneracy

Answer 15

multiple codons for 1 amino acid- this is good in case you get a mutation you might still get the right amino acid i the protein

Question 16

goal of initiation

Answer 16

assemble a ribosome with AUG and methionine tRNA in the P site so that the next amino acid can get in on the A site

Question 17

what step differs the most between proks and euks

Answer 17

initiation

Question 18

what do bacteria do in initiation

Answer 18

ribosome binds AT the start codon (thanks to the shine-delgarno sequence and 3 initiation factors IF1 2 and 3)

Question 19

eukaryotic initiation steps

Answer 19

1. elF4E binds the 7 methylguanosince ap on the 5’ end of the mRNA, 2. elFs 4G 4A 4B (etc don’t know these specifically) bind and the small ribosome binds 3. ribosome SCANS down the mRNA until it finds the AUG 4. once it has found the AUG, the large subunit can bind

Question 20

what step has the most control and regulation of this process

Answer 20

initiation

Question 21

how does elongation work

Answer 21

aminoacid-tRNA complex binds in the A site and anticodon loop base pairs with the mRNA codon that it matches

Question 22

what delivers the amino acid tRNA complex in euks? proms?

Answer 22

e- EF1A, p- Ef-Tu

Question 23

when do cells make interferon

Answer 23

virus infects cell–> cell recognizes it was infected and makes interferons–> releases them to outside of the cell–> other cells now know that a virus is around and trying to infect so they make antiviral proteins

Question 24

what 2 pathways does interferon induce

Answer 24

1. elF2 kinase to break down viral dsRNA 2. 2-5A synthase to attack viral dsRNA

Question 25

IRES sequences mean what

Answer 25

euks will use cap independent translation

Question 26

what does elF4E normally do

Answer 26

binds 4E-BP and its normal function is blocked

Question 27

what happens if you phosphorylate 4E-BP

Answer 27

it doesn’t bind elF4E and this initiates cap dependent translation

Question 28

what does rapamycin do

Answer 28

takes the phosphate off of 4E-BP so that the 4E-BP always binds elF4E–> cannot form the cap-dependent translation initiation and this blocks translation

Question 29

why do we care about elF2 alpha

Answer 29

normally this is important for binding initiator tRNA to the ribosome but if you phosphorylate it then activity is inhibited and you can’t initiate translation

Question 30

what cytokine induces elF2alpha phosphorylation

Answer 30

interfeuron- this induces the antiviral pathway (if you prevent translation in a cell then you can prevent viral RNA or DNA from getting translated)

Question 31

what protein binds iron

Answer 31

transferrin

Question 32

what transports iron into the cell

Answer 32

Transferrin Receptor (TFR)- this binds the transferrin-Fe complex into the cell when levels are low

Question 33

low iron means that transferrin receptor protein goes ____

Answer 33

up

Question 34

high iron means that the transferrin receptor protein goes

Answer 34

down

Question 35

what does ferritin do

Answer 35

sequesters excess iron and puts it in a nontoxic storage form

Question 36

low iron means what for ferritin levels

Answer 36

down

Question 37

high iron means what for ferritin levels

Answer 37

up

Question 38

what is Iron Repsonse Element (IRE)

Answer 38

RNA stem loop structure found in mRNAs that can bind to IRPs

Question 39

what are iron response binding proteins (IRE-BPs 1 and 2)

Answer 39

bind Fe and regulate expression of ferritin and TFR

Question 40

high iron conditions mean that IRE Bps are ____

Answer 40

bound to iron and thus CANNOT bind the IRE RNA so ferritin gets translated

Question 41

low iron conditions mean that IRE Bps are ____

Answer 41

NOT bound to iron so they bind to the IRE RNA and this inhibits ferritin translation