Rough ER has ribosomes attached to the continuous membrane surface and it is next to the cell nucleus, and its membrane is attached to the outer membrane of the nuclear envelope.

 

The ribosomes on rough ER are for protein synthesis, produced proteins are dispersed to the Golgi apparatus, which lies next to the ER. Some specific proteins may remain at the ER. Proteins sent to the Golgi apparatus are assembled and modified and then transported to lysosomes, the cell membrane and also may be secreted. The rough ER can also send signals to the nucleus to control protein synthesis.