The endoplasmic reticulum (ER) is a system of membranes that extends throughout the cytoplasm from the nuclear envelope to the cell membrane. ER is crucial when it comes to the transport of materials from one part of the cell to another.

Rough ER receives its name from its appearance because it has ribosomes attached to it. Proteins produced by the rough ER could potentially have carbohydrates attached to them these proteins are called glycoproteins.