The largest organelle in many cells, the endoplasmic reticulum (ER) is a network of interconnected membranous tubes and sacs that serve as locations for protein and lipid synthesis. The rough ER is covered with ribosomes where the information carried in messenger RNA molecules is translated into proteins. These newly-synthesized amino acid chains enter the lumen of the rough ER, where the proteins are modified by folding and the addition of molecules that can help target them for trafficking to different locations. The smooth ER does not have associated ribosomes (and thus looks .smooth. in electron micrographs) and is a site for lipid synthesis.
Related Molecular Functions
Related Biological Processes