The endoplasmic reticulum is a eukaryotic cellular organelle.
The endoplasmic reticulum is a network of membrane tubules (often interconnected) arranged through the cytoplasm of eukaryotic cells. Its membrane alone makes up more than half of the cell membrane system, and is in contact with the nuclear envelope.
The endoplasmic reticulum may be:
The granular endoplasmic reticulum is firstly the site of synthesis (in its associated ribosomes) of proteins secreted outside of the cell and secondly of proteins and lipids forming the cellular organelle membranes (Golgi apparatus, lysosomes, mitochondria, nucleus, ribosomes, vesicles, etc.). It contributes to the correct foldings of the proteins that have just been synthesised.
The endoplasmic reticulum is a eukaryotic organelle located in the cytoplasm. 1: nucleus; 2: nuclear pore; 3: rough endoplasmic reticulum (RER) ; 4: smooth endoplasmic reticulum (SER) ; 5: ribosome on the RER; 6: transport proteins; 7: transport vesicle; 8 : Golgi apparatus; 9 : cis face of the Golgi apparatus; 10: trans face of the Golgi apparatus ; 11: Golgi apparatus saccule. © Magnus Manske, Wikimedia, public domain