Endoplasmic Reticulum

The endoplasmic reticulum is an membrane system within the cell and is found in both animal and plant cells. It is composed of flattened sack-like structures called Cisternae. The ER is where lipid components of the cell are put together, along with many other materials transported from the cell.

Rough ER

Smooth ER

Rough ER is involved in protein synthesis. It transports synthesized proteins. It is called "rough" because of the ribosomes on is surface.

Smooth ER is "smooth" because there aren't any ribosomes on it's surface. It contains enzyme collections. Smooth ER synthesizes lipids.