What organelle is primarily involved in sorting and modifying proteins?

The Golgi apparatus is primarily involved in sorting and modifying proteins as part of the protein trafficking pathway within the cell. Once proteins are synthesized in the ribosomes and processed in the endoplasmic reticulum (ER), they are transported to the Golgi apparatus, where they undergo further modifications. This may include the addition of carbohydrate groups (glycosylation), phosphorylation, or other chemical alterations necessary for their final function.

The Golgi apparatus also plays a crucial role in sorting these modified proteins and directing them to their appropriate destinations—such as lysosomes, the plasma membrane, or for secretion outside the cell. This sorting is essential for ensuring that proteins reach the correct location to carry out their specific functions in cellular processes.

In contrast, the ribosome is the site of protein synthesis, the mitochondria are primarily responsible for energy production, and the lysosome is involved in breaking down waste materials and cellular debris rather than sorting and modifying proteins.