Endomembrane system 4/7/16 Proteins synthesized in the ER enter the endomembrane system Comprises a transport system whereby material flows between the ER, Golgi, endosomes, lysosomes, and the plasma membrane REMEMBER: Rough ER is involved in biosynthesis and processing of proteins Smooth ER is involved in drug detoxification, carbohydrate metabolism, steroid biosynthesis Network of small tubes Both water-soluble and transmembrane proteins are co-translated: Soluble ? completely translocated across the ER membrane into the lumen Default pathway = SECRETION Transmembrane ? partly translocated and will reside in the membrane Default pathway = PLASMA MEMBRANE Most proteins that enter the endomembrane system get glycosylated cytosolic proteins are generally not glycosylated