What is a characteristic of the rough endoplasmic reticulum?

The rough endoplasmic reticulum (RER) is characterized primarily by its role in the synthesis and transport of proteins. A defining feature of the RER is the presence of ribosomes attached to its cytoplasmic surface, which gives it a "rough" appearance. These ribosomes are responsible for translating messenger RNA into polypeptide chains, which are then inserted into the lumen of the RER where they undergo folding and modification.

Once synthesized, the proteins produced in the RER can be packaged into vesicles and transported to the Golgi apparatus for further processing and distribution to their eventual destinations, including secretion outside the cell, incorporation into cellular membranes, or functioning within lysosomes. This relationship between ribosomes, protein synthesis, and the RER highlights its critical role in the cell's overall function in terms of generating and processing proteins essential for various cellular activities.