What is the Endoplasmic Reticulum

The cytoplasm of most eukaryotic cells contains a very complex network of internal membranes, called the endoplasmic reticulum, which forms channels and vesicles within the cell. The endoplasmic reticulum, responsible for the synthesis of different proteins and lipids, is of two types, the smooth endoplasmic reticulum, which simply consists of membrane material and the rough endoplasmic reticulum, which is studded with a number of ribosomes. The ribosomes associated with the rough endoplasmic reticulum are actively involved in the synthesis of proteins that are meant to be exported out of the cell or that become part of the membranes. The smooth endoplasmic reticulum, lacking the ribosomes, is mainly involved in the synthesis of the lipids.