How can two types of protein synthesis in eukaryotic cells be distinguished?

The correct choice identifies that the two types of protein synthesis in eukaryotic cells can be distinguished by polyribosome types. In eukaryotic cells, there are two primary locations for protein synthesis: the endoplasmic reticulum (ER) and the cytoplasm. When ribosomes are associated with the rough ER, they form polyribosomes that synthesize proteins destined for secretion or for use in the cell membrane. In contrast, free ribosomes in the cytoplasm form different polyribosomes that synthesize proteins meant for use within the cell itself.

Thus, distinguishing between polyribosome types reflects the compartmentalization in eukaryotic cells, where different environments lead to the synthesis of different types of proteins based on their final destination and function. This understanding is fundamental to grasping how gene expression is regulated and how proteins are targeted to their appropriate cellular locales.