Which organelle is involved in the synthesis of lipids?

The endoplasmic reticulum (ER) is the correct answer because it plays a crucial role in the synthesis of lipids. It is a network of membranous tubules and sacs that is divided into two types: rough ER and smooth ER. The rough ER is studded with ribosomes and is primarily involved in protein synthesis, whereas the smooth ER lacks ribosomes and is specifically dedicated to lipid synthesis, including phospholipids and cholesterol, which are essential for membrane formation and cellular functions.

In addition to lipid synthesis, the smooth ER is also responsible for detoxification of drugs and poisons, as well as the storage of calcium ions, further emphasizing its important role in cellular metabolism. This is why the endoplasmic reticulum is central to lipid metabolism in eukaryotic cells.