Which function is characteristic of smooth endoplasmic reticulum?

• A. Protein synthesis by ribosomes.
• B. Storage of genetic material.
• C. Membrane-bound protein glycosylation.
• D. Detoxification reactions in liver.

Answer: (D)

Smooth endoplasmic reticulum specializes in detoxification and lipid-related processes. It lacks ribosomes, so it isn’t where protein synthesis by ribosomes occurs—that task is tied to the rough ER. In liver cells, smooth ER houses enzymes like cytochrome P450 that modify lipophilic toxins to make them more water-soluble for excretion. While glycosylation of proteins begins in the ER and is finished in the Golgi, those steps are not the defining feature of smooth ER. DNA storage is a nuclear function, not an ER one. So detoxification reactions in the liver best define what smooth ER does.