Endoplasmic Reticulum

The endoplasmic reticulum (ER) is an interconnected   network of membrane vesicles.  On the cytosolic face Rough endoplasmic reticulum (RER) is studded with ribosomes, secretory protein biosynthesis and the sites of membrane. Within the lumen of the RER are enzymes which involved in the posttranslational modification (proteolysis, glycosylation etc.) of membrane and secretory proteins. The smooth endoplasmic reticulum (SER) which is not studded with ribosomes is the site of phospholipid biosynthesis where a number of detoxification reactions occur.