exam 1

Question 1

location+ purpose of poly-a-tail?

Answer 1

is placed onto mRNA end + acts as signal for translation + stability

Question 2

aminoacyl tRNA synthetases + location

Answer 2

links aa to tRNA + cytoplasm

Question 3

what complex binds to 40s?

Answer 3

eIF2-tRNA^aa

Question 4

what does eIF4F do?

Answer 4

binds eIF2-tRNA^aa-40s to 5’ end of mRNA

Question 5

once eIF4F has binded what it needs to, what happens next?

Answer 5

40s is on, next comes 60s to complete the ribosome. powered by GTP hydrolysis

Question 6

EF-Tu and EF-T purposes? location?

Answer 6

help bring in next tRNA to the ribosome + cytoplasm

Question 7

EF-G purpose? location?

Answer 7

translocation, moves empty tRNA from P to E site + inside ribosome

Question 8

how is the translation process stopped?

Answer 8

RF factors come in and put a water molecule in place of the aa. they are summoned by the stop codon on the mRNA.

Question 9

How does NMD work?

Answer 9

NMD (nonsense mediated decay) is activated when an EJC (exon junction complex) is sensed on the mRNA. the EJC was supposed to be cut off along the introns, but wasnt due to premature stop codon.

Question 10

how does nonstop decay work?

Answer 10

no stop codon found, so ski7 goes into effect. it ejects the ribosome off and its presence triggers the arrival of an exosome.

Question 11

how does no go decay work? what causes it?

Answer 11

secondary structure! builds up in ribosome and stalls the ribosome. This causes an RNA degrading enzyme to come in and bind to the A site and degrades defective mRNA via nonstop decay! with exosome.

Question 12

why do free ribosomes exist?

Answer 12

they synthesize proteins that dont need ANY mods and can go directly to where they need to go

Question 13

how does the newly formed pp get to the ER? what recognizes it?

Answer 13

the new pp has a SS (signal sequence). it is recognized by SRP (signal recog. particle). the SS-SRP complex is then recog. by the SRP receptor on the exterior of the rER membrane.

Question 14

if a protein is misfolded in the ___, what does this lead to?

Answer 14

rER. leads to UPR, unfolded protein response

Question 15

!what is PERK? what does it inhibit?

Answer 15

a UPR. it inhibits eIF2 in the ribosome. this pauses translation.

Question 16

what is ERAD?

Answer 16

ER associated degradation, a UPR response. misfolded proteins are exported and degraded by proteasomes in cytosol.

Question 17

why is co-translational translocation good?

Answer 17

limits time that protein can misfold whilst getting to the rER

Question 18

rER vs sER in function?

Answer 18

rER folds proteins and deals with misfolded proteins, while sER produces lipids and steroids and does sarcoplasmic reticulum.

Question 19

!what are sarcoplasmic reticulum cells?

Answer 19

these cells are abundant in skeletal and cardiac tissues.
Ca+ ions are pumped into sER by ATP-dependent calcium ATPases during muscle contraction.

Question 20

what is the most important function of the golgi? why is it important?

Answer 20

to glycosylate. this helps prevent proteins from being degraded when outside the golgi/vesicle.

Question 21

what does the golgi consist of?

Answer 21

CGN and TGN

Question 22

how does a secretory protein vesicle get to its destination?

Answer 22

it gets to the outside of the cell by tethering and fusion. T-SNARE is a target on the plasma membrane and V-SNARE is the tag on the vesicle. They recog. each other and fuse.

Question 23

how does a protein go to the ER from the TGN?

Answer 23

it is put into a COPI vesicle with a retrieval tag KDEL on it

Question 24

how does a protein get to the CGN from the ER?

Answer 24

it is placed into a COPII coated vesicle

Question 25

what are the 3 things a mature lysosome contains?

Answer 25

H+ ATPase pump, transporters/exporters, and glycosylated proteins on the membrane

Question 26

what is a lysosomal hydrolase?

Answer 26

the characterizing enzyme inside an endosome and lysosome.

Question 27

where are lysosomal hydrolases made?

Answer 27

rER

Question 28

what is M6P? where is the receptor?

Answer 28

M6P is a tag + receptor for lysosomal hydrolase. the M6P tag goes on the pp, then the receptor on the rER membrane recognizes it to specially put it in a clathrin covered vesicle.

Question 29

what affects the M6P bond?

Answer 29

pH, when high it will dissociate

Question 30

how does a lysosome become a lysosome?

Answer 30

endosome + foreign thing in a clathrin vesicle + phagocytosis = lysosome

Question 31

what is PTS-1 and PEX-5/7?

Answer 31

receptors that bind to each other to bring it thru the peroxisome translocon

Question 32

what is the peroxisome translocon?

Answer 32

the entryway into the peroxisome

Question 33

what is a tRNA suppressor?

Answer 33

tRNA recognizes a wrongly placed stop codon (a nonsense mutation (no, we cant stop the show now! Its nonsense)) and insert a functional aa in its place, suppressing the nonsense mutation.