The right answer is synthesize large quantities of lipids.
It should be known that there are two types of endoplasmic reticulum: rough (contains ribosomes) and smooth (does not contain ribosomes).
The rough endoplasmic reticulum harvests in its light the proteins synthesized by the ribosomes attached to its surface. The proteins then move inside the light to be eventually transported to the Golgi apparatus, where they will complete their maturation and be distributed to the different compartments of the cell.
The smooth endoplasmic reticulum carries, associated with its membrane, the enzymes necessary for the synthesis of lipids and lipoproteins (molecules associating a protein part and a lipid part). Very reduced in the majority of cells, the smooth endoplasmic reticulum is very extensive in cells specialized in the synthesis of lipids (adipocytes) or in that of lipoproteins (hepatocytes for example).
