Endoplasmic reticulum is an organelle found in both eukaryotic animal and plant cells. It often appears as two interconnected sub-compartments, namely rough ER and smooth ER. Both types consist of membrane enclosed, interconnected flattened tubes.
The endoplasmic reticulum is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum, and smooth endoplasmic reticulum. It usally has ribosomes attatched to it.