Which structure is primarily responsible for the synthesis of lipids?

The smooth endoplasmic reticulum (SER) is primarily responsible for the synthesis of lipids. This organelle lacks ribosomes on its surface, which differentiates it from the rough endoplasmic reticulum that is involved in protein synthesis. The smooth ER plays a crucial role in synthesizing phospholipids and cholesterol, which are essential components of cellular membranes. Additionally, the smooth ER is involved in the metabolism of carbohydrates, detoxification of drugs and poisons, and storage of calcium ions.

Due to its specialized membrane structure and extensive network within the cell, the smooth endoplasmic reticulum facilitates these various lipid-related processes efficiently, making it the key player in lipid synthesis within the cell.