Final answer:
The major site of lipid synthesis in eukaryotic cells is the endoplasmic reticulum (ER), specifically the smooth endoplasmic reticulum (SER).
Step-by-step explanation:
The major site of lipid synthesis in eukaryotic cells is the endoplasmic reticulum (ER). Specifically, the smooth endoplasmic reticulum (SER) is involved in the synthesis of lipids including phospholipids and cholesterol.
The smooth endoplasmic reticulum functions in lipid metabolism, carbohydrate metabolism, detoxification of drugs and poisons, and storage of calcium ions. The SER is distinguished from the rough endoplasmic reticulum (RER), which is characterized by the presence of ribosomes on its surface and is primarily involved in protein synthesis. The lipid synthesis in the SER includes the production of fatty acids through lipogenesis in the cytoplasm and transferred to the ER for further processing. Once synthesized, lipids can be distributed to various parts of the cell and are also used to form the bi-layer of the cell membrane. This makes the smooth ER critically important for cellular function as lipids are fundamental components of all cell membranes and are used for energy storage and signaling.