Final answer:
Ribosomes that synthesize secretory proteins are bound to the rough endoplasmic reticulum and ensure that these proteins are sequestered from the cytosol and sent to their specific destinations. Cytosolic protein-synthesizing ribosomes and these proteins serve functions within the cytosol itself.
Step-by-step explanation:
The question pertains to the differences between ribosomes that synthesize secretory proteins versus those that make cytosolic proteins. Ribosomes, which are essential for protein synthesis, can be either bound to the rough endoplasmic reticulum (RER) or free-floating in the cytosol. The key difference lies in the proteins' destination: secretory proteins, membrane proteins, and proteins destined for organelles are synthesized on ribosomes bound to the RER. These proteins enter the RER as they are synthesized and are sequestered from the cytosol. In contrast, cytosolic proteins are made on ribosomes that are free in the cytoplasm, and these proteins typically remain within the cytosol after their synthesis.
Once synthesized, secretory proteins are directed to the Golgi apparatus, where they undergo further modifications. After this process, they are sorted and sent to their final destinations, which could include being secreted out of the cell, incorporated into the cell membrane, or directed to other organelles. Therefore, while all ribosomes perform the same general function of protein synthesis, it is their location and the fate of the proteins they synthesize that distinguishes ribosomes involved in the production of secretory and membrane proteins from those producing cytosolic proteins.