Rough ER and protein synthesis

Question 1

where does protein synthesis happen?

Answer 1

in the cytosol

Question 2

how do ribosomes exist

Answer 2

in a common pool; assemble with mRNA when translation needs to happen

Question 3

polysome

Answer 3

multiple ribosomes associated with reading a message. also bound to ER membrane.

Question 4

ER signal sequence

Answer 4

recognized by signal recognition particle. translation is temp paused and whole assembly is brought to surface of ER. SRP receptor on surface association and translation continues at this point. translation is made and goes through ribosome, translocon, and into ER lumenal unit.

Question 5

The signal hypothesis

Answer 5

N terminal signal cleaved by signal peptidase facing ER lumen. how do we know soluble protein had a signal.

Question 6

how does SRP work

Answer 6

just floating around. binds signal peptide and delivers the translational machinery to the ER membrane for continued translation and translocation

Question 7

to what on ER membrane does SRP deliver ribosome?

Answer 7

to a protein translocator on the membrane

Question 8

what happens after SRP delivers ribosome to translocator?

Answer 8

SRP is released and recycled. translation continues and translocation begins.

Question 9

what is translocon?

Answer 9

protein translocator

Question 10

process of translocation of soluble protein across the ER membrane?

Answer 10

a. start with inactive translocon and signal attached to N terminal of soluble protein
b. signal attaches to translocon and it becomes activated
c. signal peptidase attaches to protein/translocon unit
d. signal is cleaved and mature soluble protein is released from translocon