The Endoplasmic reticulum is a network of membranous tubules within the cytoplasm of a eukaryotic cell. They are of two types;
Smooth endoplasmic reticulum
Rough endoplasmic reticulum
The smooth endoplasmic reticulum is a membrane-bound network of tubules without ribosomes. Unlike the rough endoplasmic reticulum, the smooth endoplasmic reticulum is not involved with protein synthesis. Its primary function is to synthesize lipids, steroids, carbohydrates, and the metabolism of drugs or toxins.