What does the smooth endoplasmic reticulum (ER) mainly synthesize?

The smooth endoplasmic reticulum (ER) is primarily involved in the synthesis of lipids. This organelle plays a crucial role in producing phospholipids and cholesterol, which are essential components of the plasma membrane. Furthermore, the smooth ER is also responsible for the biosynthesis of steroid hormones in certain cell types, emphasizing its role in lipid metabolism.

In addition to lipid synthesis, the smooth ER is implicated in detoxifying certain chemicals and storing calcium ions, but its primary function remains the production of lipids that are vital for maintaining the structural integrity and functionality of biological membranes. The synthesis of lipids for the plasma membrane is critical as it allows for the dynamic nature of membranes, contributing to cell signaling, transport, and cellular compartmentalization.