The Smooth Endoplasmic Reticulum synthesizes lipids, phospholipids, and steriods. The Smooth Endoplasmic Reticulum is connected to the nuclear envelope's outer membrane.
The Rough Endoplasmic Reticulum is covered with ribosomes. Its main functions are to manufacture lysosomal enzymes and secreted proteins. The Rough Endoplasmic Reticulum is connected to the outer membrane of the nuclear envelope.