Which statement describes smooth endoplasmic reticulum?

• A. It has ribosomes on its surface.
• B. It is involved in DNA storage.
• C. It has no associated ribosomes.
• D. It produces energy for the cell.

Answer: (C)

Smooth endoplasmic reticulum is defined by the absence of ribosomes on its surface, giving it a smooth appearance. This lack of ribosomes differentiates it from the rough ER, which is studded with ribosomes and specializes in making proteins for secretion and for membranes. Functionally, the smooth ER is involved in lipid synthesis, certain carbohydrate metabolism tasks, detoxification processes, and calcium storage in muscle cells. It does not produce energy (that’s the role of mitochondria) and it does not store DNA (that’s in the nucleus). Therefore, the statement that describes it best is that it has no associated ribosomes.