What is the role of the Golgi apparatus in a cell?

The Golgi apparatus plays a crucial role in the processing and transport of proteins within a cell. Its primary functions include modifying proteins that have been synthesized in the endoplasmic reticulum, sorting these proteins based on their final destinations, and packaging them into vesicles for transport to various locations, either within the cell or outside of it. This modification can involve the addition of carbohydrate groups (glycosylation) or other changes that are necessary for the proper functioning of proteins.

In contrast, synthesizing lipids is mainly the function of the smooth endoplasmic reticulum, while energy production occurs in the mitochondria through cellular respiration. The storage of waste products is typically handled by lysosomes and other cellular compartments designed for waste management. Therefore, the Golgi apparatus's unique role in the cellular processes of modification, sorting, and packaging of proteins is what makes this option the correct answer.