Which organelle modifies, sorts, and packages proteins for secretion?

• A. Lysosome
• B. Endoplasmic reticulum
• C. Golgi apparatus
• D. Nucleus

Answer: (C)

The Golgi apparatus processes proteins for secretion. After synthesis and initial folding in the rough endoplasmic reticulum, proteins are transported to the Golgi in vesicles. There, they undergo chemical modifications (like adding sugar groups) and are sorted and packaged into new vesicles. These vesicles then target the proteins either to the plasma membrane for secretion, to become membrane proteins, or to lysosomes as enzymes. When secretion occurs, the secretory vesicles fuse with the cell membrane and release their contents outside the cell.

Proteins that stay inside the cell or are used for other organelles aren’t sent to the Golgi for secretion; for example, lysosomes contain digestive enzymes, the ER is where synthesis and folding start, and the nucleus houses genetic material.