Smooth Endoplasmic Reticulum
Smooth Endoplasmic Reticulum

Smooth Endoplasmic Reticulum

In contrast to the RER, smooth endoplasmic reticulum lacks ribosomes and is not involved in protein synthesis. Note that the lack of ribosomes means that the smooth ER is not basophilic and usually stains poorly by H&E. The main functions of SER are the biosynthesis of phospholipids and cholesterol and the synthesis and repair of membranes. It also possesses some tissue-specific functions: in the liver, the SER contains large amounts of cytochrome P450 and participates in the detoxification of metabolic waste products, drugs, and alcohol; in the muscle, the SER is known as the sarcoplasmic reticulum and stores and releases calcium ions needed for muscle contraction. Although the composition and function of the smooth ER is different than the rough ER, they are continuous with each other. In what types of cells, besides liver and muscle, would you expect to find large amounts of smooth ER?