The Fundamental Unit of Life — Science STD 9 — Question

4. All of the above

Explanation:
The endoplasmic reticulum is a system of membrane-lined channels found in all eukaryotic cells except mature erythrocytes.
Rough endoplasmic reticulum carries ribosomes on their surface and is involved in the protein synthesis of proteins.
Smooth endoplasmic reticulum lacks ribosomes. Smooth endoplasmic reticulum occurs in cells engaged in producing lipids and steroid hormones.
SER, in the liver also helps in the detoxification of organic compounds.