is rough er part of the endomembrane system
Endomembrane system Many types of cells export proteins produced by ribosomes attached to the rough ER. The ribosomes assemble amino acids into protein units, which are carried into the rough ER for further adjustments. These proteins may be either transmembrane proteins, which become embedded in the membrane of the endoplasmic reticulum, or water-soluble proteins, which are able to pass through the membrane into the lumen. Those that reach the inside of the endoplasmic reticulum are folded into the correct three-dimensional conformation. Chemicals, such as carbohydrates or sugars, are added, then the endoplasmic reticulum either transports the completed proteins, called secretory proteins, to areas of the cell where they are needed, or they are sent to the Golgi apparatus for further processing and modification.[23][26]
Endomembrane system Most lipids are synthesized in yeast either in the endoplasmic reticulum, lipid particles, or the mitochondrion, with little or no lipid synthesis occurring in the plasma membrane or nuclear membrane.[12][13] Sphingolipid biosynthesis begins in the endoplasmic reticulum, but is completed in the Golgi apparatus.[14] The situation is similar in mammals, with the exception of the first few steps in ether lipid biosynthesis, which occur in peroxisomes.[15] The various membranes that enclose the other subcellular organelles must therefore be constructed by transfer of lipids from these sites of synthesis.[16] However, although it is clear that lipid transport is a central process in organelle biogenesis, the mechanisms by which lipids are transported through cells remain poorly understood.[17]