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Question 1

Structure of secretory cells in pancreas

Answer 1

Polarity taken into account, nucleus and RER cisternae near basal surface, facing cytoplasm. Apical surface faces duct that carries proteins out of organ

Question 2

RER functions

Answer 2

Synthesis of most membrane lipids, beginning of addition of sugars to asparagine residues of proteins

Question 3

What determines where proteins are synthesized?

Answer 3

Secretory proteins have signal sequences at N-Terminus that directs polypeptide and ribosome to ER. Polypeptides move into cisternal space of ER through protein lined AQ channels in ER membrane.

Question 4

Co translational translocation

Answer 4

The release of proteins from cytosololic side of RER to lumen

Question 5

How are secretory, lysosomal, or plant vacuolar proteins synthesized

Answer 5

Cotranslational translocation-
Newly forming proteins put in ER lumen by ER membrane bound ribosome. Synthesis of polypeptide begins after mRNA binds to free ribosome. Polypeptides that undergo cotranslational translocation have a signal sequence of 6-15 hydrophobic AAs that help polypeptides fold.

Question 6

What happens after secretory/lysosomal/vacuolar proteins are synthesized?

Answer 6

After it emerges from the ribosome, the hydrophobic signal sequence is recognized and binds to a signal recognition particle. It’s brought to the ER membrane and handed to the translocon. Polypeptide works its way through the translocon, displacing plug.

Question 7

What proteins are also involved in synthesis and trafficking of secretory proteins?

Answer 7

GTP/G binding proteins (Different names for the same thing)- Can also act like molecular switches. Hydrolysis of bound GTP turns off protein