Final answer:
Newly synthesized phospholipids are primarily inserted in the endoplasmic reticulum(ER) before being distributed to their proper destinations. The Golgi apparatus plays a role in further modifying these phospholipids.
Step-by-step explanation:
The primary location where newly synthesized phospholipids are inserted is the endoplasmic reticulum (ER). The ER modifies proteins and synthesizes phospholipids that are used in cell membranes. These phospholipids are then transported to the Golgi apparatus where they undergo further modifications before being distributed to their proper destinations, including the cell membrane.