At one time, the cell was considered a fairly random place, without much structure. Of course that is no longer the view. First discovered in 1945, the endoplasmic reticulum (ER) is one of the more complex organelles found within eukaryotic cells. It has been differentiated into a “rough endoplasmic reticulum" (RER) and a “smooth endoplasmic reticulum" (SER). These function somewhat differently, with one primarily involved in protein manufacture and the other supplying needed ions and steroids. To gain more knowledge and insight into the structure and function of the endoplasmic reticulum, be sure to read articles written by informed Bright Hub contributors.
Photo: NIH - Protein Glycosylation in the RER