The organelle that modifies and packages proteins is the Golgi apparatus. This organelle comprises several flattened sacs called cisternae. The Golgi apparatus, also called the Golgi body or Golgi complex, has two sides or faces, the cis face and the trans face, as described in "The Cell: A Molecular Approach."
The Golgi apparatus retrieves proteins carried in vesicles made in the endoplasmic reticulum. The organelle then modifies these proteins by chopping off some sections or adding necessary molecules. A vesicle then forms around the protein, pinches off of the Golgi apparatus and travels to where the protein is needed. The cis face of the Golgi apparatus lies near the endoplasmic reticulum to receive its products. The trans face of the organelle is positioned near the plasma membrane, ready to transport the finished protein out of the cell.