What is the role of the Golgi apparatus in protein processing and routing?

• A. The Golgi modifies proteins (e.g., glycosylation), sorts them, and packages them into vesicles for secretion, delivery to lysosomes, or residence in membranes.
• B. The Golgi generates ATP for cellular energy.
• C. The Golgi degrades misfolded proteins.
• D. The Golgi is the primary site of protein translation.

Answer: (A)

The Golgi apparatus functions as the main processing and routing center for proteins after they are made in the endoplasmic reticulum. As proteins move through its stacked cisternae, the Golgi enzymatically modifies them—most notably by adding and trimming carbohydrate groups (glycosylation) and sometimes attaching other tags that help determine their final destination. These modifications create the molecular “addresses” that guide where a protein should go next. In the trans-Golgi network, the proteins are sorted and packaged into distinct vesicles tailored for specific routes: secretion outside the cell, delivery to lysosomes, or incorporation into the plasma membrane. For example, lysosomal enzymes often receive a mannose-6-phosphate tag that targets them to lysosomes, while secreted proteins are packed into vesicles that fuse with the cell surface to release their contents.

ATP production happens in mitochondria, not the Golgi. Degradation of misfolded proteins is primarily handled by quality-control pathways in the ER and by proteasomes or lysosomes downstream, not by the Golgi itself. Protein translation occurs on ribosomes, not in the Golgi.