Endoplasmic Reticulum
About 50% of the cells total membrane surface is composed of endoplasmic reticulum (ER), that manufactures proteins and lipids that are exported to other cells. There are two type of ER, smooth (SER) and rough (RER), RER has ribosomes on the outside of it. thus giving it a rough look. The endoplasmic reticulum was discovered in 1945 by a man named Albert Claude.Also, in the 1950's a man named George Palade discovered the amount of rough endoplasmic reticulum is related to how many proteins the cell produces.