What is a key role of the smooth endoplasmic reticulum (smooth ER)?

The smooth endoplasmic reticulum (smooth ER) is primarily involved in lipid synthesis, which includes the production of phospholipids and cholesterol that are essential for cellular membranes and signaling molecules. Unlike the rough endoplasmic reticulum, which is studded with ribosomes and is primarily responsible for protein synthesis, the smooth ER is devoid of these ribosomes. Instead, its structure and enzymatic activity are specialized for the synthesis and metabolism of lipids. This function is critical for cell growth, cell membrane formation, and the overall maintenance of cellular structures, making lipid synthesis a key role of the smooth ER. Additionally, the smooth ER also plays a role in detoxifying certain chemicals and storing calcium ions, but its primary identity is linked to lipid metabolism.