Which sequence best describes the flow of proteins in the secretory pathway?

The sequence that reflects the correct flow of proteins in the secretory pathway is the one that starts from the Rough Endoplasmic Reticulum (Rough ER), progresses through the Golgi apparatus, and then moves to secretory vesicles before being transported to the exterior of the cell.

In this process, proteins synthesized by ribosomes attached to the Rough ER are co-translationally imported into the ER lumen, where they undergo folding and post-translational modifications. Subsequently, these proteins are packed into vesicles that bud from the ER and are sent to the Golgi apparatus. Within the Golgi, proteins are further processed and sorted for their final destinations. The properly modified proteins are then transported in secretory vesicles that ultimately fuse with the plasma membrane, releasing their contents outside the cell.

This pathway is fundamental for the secretion of proteins such as hormones, enzymes, and antibodies, making it crucial for normal cellular and physiological function. The other sequences listed either describe incorrect pathways or involve organelles not typically engaged in the secretory process.