Final answer:
The endomembrane system includes several cellular components that work together. The chloroplast is not part of this system.
Step-by-step explanation:
The endomembrane system includes the nuclear envelope, lysosomes, vesicles, the ER, and Golgi apparatus, as well as the plasma membrane. These cellular components work together to modify, package, tag, and transport proteins and lipids that form the membranes.
The structure that is not part of the endomembrane system is the chloroplast. Chloroplasts are organelles involved in photosynthesis and are not part of the endomembrane system.