Which organelle is responsible for modifying proteins by adding or removing chemical groups?

The Golgi apparatus is the organelle responsible for modifying proteins by adding or removing chemical groups. This organelle functions as a processing and packaging center for proteins that have been synthesized in the rough endoplasmic reticulum. After proteins are transported to the Golgi apparatus, they undergo various modifications, such as glycosylation (adding carbohydrate groups) or phosphorylation (adding phosphate groups), which are crucial for their functionality and destination within the cell.

The modifications made by the Golgi apparatus are essential for the proper functioning of proteins, as they determine how proteins are folded, how they interact with other molecules, and where they are ultimately delivered, whether it's to the plasma membrane, secretory vesicles, or lysosomes. This precise modification process is crucial for maintaining the overall health and functionality of cellular processes.