This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure and function of protein, Subject name: Biochemistry
Secretory proteins are synthesized in 
Select and explain. 
A. Cytoplasm, B. Endoplasmic Reticulum, C. First in cytoplasm and then in Endoplasmic Reticulum, D. First in Endoplasmic Reticulum and then in cytoplasm
B: Endoplasmic Reticulum
Answer: B: Endoplasmic Reticulum 
Explanation: ER is a network of interconnecting membranes enclosing channels or cisternae, that are continuous from outer nuclear envelope to outer plasma membrane. This will be very prominent in cells actively synthesizing proteins,e.g.immunoglobulin secreting plasma cells. The proteins , glycoproteins and lipoproteins are synthesised in the ER. REFERENCE:DM.VASUDEVAN.Textbook. SEVENTH EDITION ; PAGE NO 12