An important organelle in the Eukaryota cells is the Endoplasmic Reticulum (ER). It is important for the cells because it plays the key role in the construction, processing, and transport of some proteins and lipids that are necessary for the living body. The ER is responsible for the production of transmembrane proteins and lipids for the cell membrane and also for some important components of the cell including the Golgi apparatus, lysosomes, plant cell vacuoles, secretory vesicles etc.