What type of polyribosome is involved in eukaryotic protein synthesis?

In eukaryotic cells, polyribosomes, or polysomes, can be found in both free and membrane-bound forms, reflecting the diversity and versatility of protein synthesis in these organisms. Free ribosomes are found floating in the cytoplasm and primarily synthesize proteins that function within the cytosol, such as enzymes and structural proteins. On the other hand, membrane-bound ribosomes are attached to the endoplasmic reticulum (ER), specifically the rough ER, and are responsible for producing proteins that are either secreted from the cell or incorporated into cellular membranes.

The presence of both types of polyribosomes allows eukaryotic cells to efficiently synthesize a wide array of proteins tailored to their specific functional needs. For instance, proteins destined for secretion or for use in the cell membrane are synthesized by the ribosomes on the ER, while those needed for use within the cell itself can be synthesized by free ribosomes. This dual system enhances the adaptability and functionality of eukaryotic cells. Therefore, the correct answer accurately reflects the complex processes at play in eukaryotic protein synthesis.