Are they produced by RER-bound ribosomes or by free ribosomes and later they get imported into the SER.
Also, how does the ER separate enzymes that work in the RER (e.g. glycosylases) from enzymes that work in the SER (e.g. detoxifying enzymes)? I know sometimes the ER is “mixed” so could be considered as rough and smooth at the same time, but let’s say when the two parts are obviously both stucturally and functionally are separate parts.