Secretion vesicles are not considered a part of the biosynthesis process. There are two reasons for this:

1. Secretion vesicles do not make any molecules. They simply hold and then secrete them. Biosynthesis is the making of molecules.

2. MOST biosynthesized molecules are not secreted. They are used by the cell. Thus, secretion vesicles are not essential for biosynthesis. They are only essential for secretion.