Secretory proteins and membrane molecules are synthesized mainly by the

Answer;

-The rough endoplasmic reticulum /

Secretory proteins and membrane molecules are synthesized mainly by the rough ER.

Explanation;

-The rough ER plays a central role in the synthesis and export of proteins and glycoproteins and is best studied in the secretory cells specialized in these functions.

-Rough ER is found throughout the cell but the density is higher near the nucleus and the Golgi apparatus. Ribosomes on the rough endoplasmic reticulum are responsible for the manufacture of protein through a process of translation.