Endoplasmic Reticulum

The endoplasmic reticulum is the organelle in which components of the cell membrane are assembled and some proteins are modified. The rough endoplasmic reticulum (called this because of the ribosomes littering its surface) is involved in the synthesis of proteins. The smooth endoplasmis reticulum, which is free of ribosomes, contains collections of enzymes that perform specialized tasks, such as the synthesis of lipids.