The rough endoplasmic reticulum (ER) is the site of protein synthesis and the smooth ER is the site of lipid synthesis. What is the third compartment of the endomembrane system, and what is that compartment's function?

Answer: Golgi apparatus.

Explanation: Proteins are manufactured in the rough endoplasmic reticulum, the manufactured protein travel to the Golgi body where

they are processed and sent throughout the entire cell.

The main function of the Golgi apparatus is modifying, sorting and packaging of proteins for secretion. The sacs or folds of the Golgi apparatus are called cisternae.