To fill in the blanks in the passage accurately, we need to understand the functions of the rough endoplasmic reticulum (RER) and Golgi apparatus.
The rough endoplasmic reticulum is primarily involved in protein synthesis (production), while the Golgi apparatus is responsible for packaging and modifying these proteins for transport to various parts of the cell or for secretion.
Given those roles, the correct answer to fill in the blanks would be "protein making and protein packaging."
So, the completed passage would read:
"Proteins are important molecules that are synthesized, transported, and used by cells in a multitude of ways. The rough endoplasmic reticulum and Golgi apparatus have parts to play in the system. These functions are protein making and protein packaging, respectively."