The organelle involved in packaging and transporting proteins is the Golgi apparatus. This complex of membrane-bound sacs modifies, sorts, and packages proteins and lipids synthesized in the endoplasmic reticulum for secretion or delivery to specific cellular locations. The Golgi apparatus plays a critical role in the cellular secretion pathway by ensuring that proteins are correctly processed and adequately modified with carbohydrate groups and other molecules essential for their function. It is pivotal in maintaining cellular organization and protein distribution.