in a typical growing cell that is dividing once every 24 hours, the equivalent of one new plasma membrane must transit the ER every day. If the ER membrane is 40 times the area of plasma membrane, what is the ratio of plasma membrane proteins to other proteins in the ER? Assume that all proteins on their way to other compartments remain in the ER for 30 minutes on average before exiting, and that the ratio of proteins to lipids in the membranes of all compartments is the same.