What is the main function of the Golgi apparatus?

The main function of the Golgi apparatus is to modify, sort, and package proteins received from the endoplasmic reticulum (ER). This organelle plays a crucial role in processing proteins that are destined for secretion, incorporation into the cell membrane, or delivery to other organelles. Once proteins are synthesized in the rough ER, they are transported to the Golgi apparatus, where they undergo various modifications, such as glycosylation (the addition of sugar molecules), phosphorylation, or cleavage.

After these modifications, the Golgi apparatus sorts the proteins to ensure they are delivered to the correct location within or outside the cell. This process is essential for maintaining cellular functions and facilitating communication between cells. The Golgi apparatus acts like a shipping and receiving center, ensuring that proteins are correctly processed and sent to their designated destinations.

Other processes mentioned in the options, like synthesizing DNA, breaking down waste materials, or producing energy, pertain to different cellular organelles and functions, such as the nucleus for DNA synthesis, lysosomes for waste breakdown, and mitochondria for energy production. Therefore, the Golgi apparatus's primary role is distinct and vital for protein processing and transport within the cell.