A certain organelle is part of the endomembrane system of a cell and looks like flattened sacs of membranes. It is often referred to as the "post office" of the cell because it sorts, modifies, and repackages proteins and lipids. It then ships the products in vesicles to other parts of the cell or to the plasma membrane, where they may exit the cell. However, this organelle does not participate in the synthesis of proteins and lipids. Identify this organelle.

The endomembrane system includes the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, several types of vacuoles, and the plasma membrane.

The Golgi apparatus consists of flattened membranous sacs called cisternae. They are stacked upon each other. The membrane of each cisterna in a stack maintains the unique internal space from the cytosol. Proteins and lipids formed on the ER are packed in many transport vesicles and are delivered to the Golgi apparatus.

The Golgi apparatus serves as a site for modification, and packaging of proteins and lipids. Modification of proteins in the Golgi apparatus results in the formation of several types of modified biomolecules such as glycoproteins. It serves as the site for the packaging of secreted proteins and sorting of other proteins to vacuoles and other organelles via transport vesicles. The transport vesicles carrying various biomolecules are formed in the trans face of the Golgi apparatus. These vesicles pinch off from the Golgi membrane and transport their contents to a specific destination.