What cellular structure is responsible for packaging and modifying proteins?

The Golgi apparatus is a crucial cellular structure involved in the packaging, modification, and sorting of proteins and lipids that have been synthesized in the endoplasmic reticulum (ER). Once proteins are produced in the rough ER, they are transported to the Golgi apparatus, where they undergo further modifications, such as glycosylation or phosphorylation. This process is essential for ensuring that proteins are correctly folded and functional for their specific roles in the cell or for export to other locations in the organism.

After processing, the Golgi apparatus sorts and packages these proteins into vesicles that can be directed to various destinations, including secretion outside the cell, delivery to lysosomes, or incorporation into the plasma membrane. This function establishes the Golgi apparatus as the central hub for protein trafficking and maturation in the cell, making it a key player in cellular function and communication.