Final answer:
The rough appearance of the ROUGH ER is due to the presence of ribosomes on its surface, which are responsible for protein synthesis and give it a studded texture when viewed through an electron microscope.
Step-by-step explanation:
The rough appearance on the ROUGH ER is due to the association of ribosomes. When viewed through an electron microscope, the rough endoplasmic reticulum (RER) displays a studded texture because it has ribosomes attached to its cytoplasmic surface. These ribosomes are engaged in the process of translating proteins directly into the lumen of the RER, thus contributing to its rough appearance.
In contrast to the smooth endoplasmic reticulum, which has varied functions like lipid synthesis and detoxification, the rough ER is specialized for the synthesis and modification of proteins that are either integrated into the cell membrane or exported. Proteins synthesized by the ribosomes on the rough ER are often glycosylated before being transported to the Golgi apparatus for further processing and packaging.