When this set of slides, we're going to look at rough endoplasmic reticulum, which are the bound ribosomes, which synthesize proteins that are going to be sequestered from cytoplasm in lysosomes or similar organelles, that are going to be secreted from the cell, or that are actually going to end up as membrane proteins embedded in cellular membranes. In eukaryotic cells, bound ribosomes are attached to membranes of the rough endoplasmic reticulum, or RER, which is actually continuous with the outer membrane of a nuclear envelope. The RER is typically situated in cells near the nucleus on the one hand and near Golgi vesicles on the other. The RER can assume a variety of shapes like the whorled form at the upper left in this slide. The TEM at the upper right shows a nucleus surrounded by lots of RER, and the lower electron micrograph shows RER in the vicinity of Golgi vesicles. The association of RER with Golgi vesicles is related to the fact that the protein synthesized and packaged in the rough endoplasmic reticulum usually travel to the Golgi vesicles for further processing before they reach their final destination.