If a cell is unable to synthesize lipids, the organelle that might be defective is the smooth endoplasmic reticulum (option 1). The smooth endoplasmic reticulum (ER) is responsible for lipid synthesis in the cell. It contains enzymes that catalyze the various steps of lipid synthesis, including the production of phospholipids, cholesterol, and steroids. It also plays a role in detoxification and calcium storage.

On the other hand, option 2 (Golgi bodies) is not directly involved in lipid synthesis. The Golgi bodies are responsible for modifying, sorting, and packaging proteins and lipids into vesicles for transportation within the cell.

Option 3 (Lysosomes) is involved in the breakdown of macromolecules and waste materials within the cell. It does not have a direct role in lipid synthesis.

Option 4 (Mitochondria) is the powerhouse of the cell and is primarily involved in energy production through cellular respiration. While mitochondria play a role in lipid metabolism, they are not primarily responsible for lipid synthesis in the cell.

Therefore, if a cell is unable to synthesize lipids, it is likely that the smooth endoplasmic reticulum is defective.