Final answer:
ER-resident proteins can be retrieved from the Golgi apparatus if they mistakenly get transported there, after which they are recognized by retrieval mechanisms and returned to the RER.
Step-by-step explanation:
ER-resident proteins can be retrieved from the Golgi apparatus if they make it that far. Once in the Rough Endoplasmic Reticulum (RER), proteins undergo modifications such as folding or addition of side chains. If these modified proteins are not meant to remain in the RER, they are packaged within vesicles for transport. These transport vesicles then bud from the RER and travel to the Golgi apparatus, where they may undergo further modifications and sorting.
Proteins destined for secretion, or incorporation into cellular membranes, then move from the cis to the trans face of the Golgi apparatus. Sorting proteins in the trans Golgi vesicles guide these processed proteins to their final destinations within the cell. However, if ER-resident proteins accidentally travel to the Golgi apparatus, the cell has retrieval mechanisms involving specific signals that can recognize and return them back to the RER.