Cell Structure and Cell Organelles
The Endoplasmic Reticulum
The endoplasmic reticulum (ER) is a network of membrane-bound tubes and cisternae connected to the cell nucleus through the nuclear pores. It pervades the entire cell. The rough ER is covered by ribosomes (RER); the smooth ER is not. The ER modifies proteins and transfers substances to the Golgi apparatus.
German-born American Günter Blobel won the 1999 Nobel Prize in Physiology and Medicine for the discovery "that proteins have intrinsic signals that govern transport and localization in cells".