What are sacs that contain meterials in a eukaryotic cell?
That would be a vesicle which is either formed by allowing
external materials in (Endocytosis), or it is also formed by the
Golgi Apparatus placing a phospholipid bi-layer around the protein
produced in the Endoplasmic Reticulum, then the vesicle releases
the protein to the outside of the cell in a process called
Exocytosis.