Which organelle is involved primarily in lipid synthesis?

The smooth endoplasmic reticulum (Smooth ER) is the organelle primarily responsible for lipid synthesis. Unlike its counterpart, the rough endoplasmic reticulum, which has ribosomes on its surface and is primarily involved in protein synthesis, the smooth ER lacks these ribosomes and is dedicated to the production of lipids. It plays a crucial role in the biosynthesis of phospholipids, cholesterol, and steroid hormones, making it essential for maintaining the cell membrane's structure and producing signaling molecules.

In addition to lipid synthesis, the smooth ER is also involved in the metabolism of carbohydrates and the detoxification of drugs and poisons. This multifunctionality underscores the significance of the smooth ER in cellular lipid homeostasis and overall cellular function.