Final answer:
The Smooth Endoplasmic Reticulum (SER) is responsible for the synthesis of lipids, including phospholipids, in the cell.
Step-by-step explanation:
The organelle involved in the synthesis of fat or lipids for the cell, such as phospholipids, is the Smooth Endoplasmic Reticulum (SER). The SER synthesizes carbohydrates, lipids, including phospholipids and cholesterol, and steroid hormones; it also plays a role in the detoxification of medications and poisons, and stores calcium ions. In contrast, the Rough Endoplasmic Reticulum (RER) is primarily associated with protein synthesis, as it has ribosomes attached to its surface. The Golgi Apparatus, on the other hand, is involved in the modification, sorting, tagging, and packaging of proteins and lipids for secretion or use within the cell.