Which of the following sequences for the processing of proteins produced within the cell is correct?

• A. Plasma membrane → Secretory vesicles → Golgi apparatus → Rough ER
• B. Secretory vesicles → Rough ER → Golgi apparatus → Plasma membrane
• C. Golgi apparatus → Rough ER → Secretory vesicles → Plasma membrane
• D. Rough ER → Golgi apparatus → Secretory vesicles → Plasma membrane

Answer: (D)

Verified step by step guidance

1. Begin by understanding the role of each organelle involved in protein processing within the cell. The Rough Endoplasmic Reticulum (Rough ER) is where protein synthesis occurs, especially for proteins destined for secretion or for use in the cell membrane.
2. Next, recognize that after synthesis in the Rough ER, proteins are transported to the Golgi apparatus. The Golgi apparatus functions as a packaging and modification center, where proteins are further processed, sorted, and prepared for their final destinations.
3. After processing in the Golgi apparatus, proteins are packaged into secretory vesicles. These vesicles are responsible for transporting the proteins to their next destination, which could be the plasma membrane or outside the cell.
4. Finally, the secretory vesicles fuse with the plasma membrane, releasing their contents outside the cell or incorporating proteins into the cell membrane. This step completes the journey of proteins from synthesis to secretion or membrane integration.
5. Review the sequence: Rough ER → Golgi apparatus → Secretory vesicles → Plasma membrane. This is the correct order for the processing of proteins produced within the cell, ensuring they are properly synthesized, modified, and transported to their final destination.