Endoplasmic Reticulum

The endoplasmic reticulum exists in two forms that differ both in appearance and in function. Smooth endoplasmic reticulum lacks ribosomes on its surface and is the principal site of lipid and steroid synthesis, as noted in NCERT Class 11, Chapter 8 (Cell: The Unit of Life); cells active in producing fats and steroid hormones, such as liver cells, therefore develop extensive smooth ER. Rough endoplasmic reticulum is incorrect because the ribosomes attached to its surface make it specialised for protein synthesis and secretion rather than lipid production. The option naming only Golgi cisternae is misleading, since the Golgi apparatus mainly modifies, packages and dispatches materials rather than synthesising lipids in bulk. Free cytoplasmic ribosomes synthesise proteins that usually remain within the cell and have no direct role in steroid manufacture. A functional consistency check supports the choice: a cell specialised for lipid and steroid output must expand the organelle that carries the enzymes for those pathways, and that organelle is the smooth endoplasmic reticulum.