A complex interconnecting system of flattened membrane-surrounded channels and vesicles (cisternae) that spreads throughout the cytoplasm of eukaryotic cells. The membranes appear to be continuous with the * plasma membrane at the outer surface and with the * tonoplast and * nuclear membrane, and have the same general structure. Some cisternae have a granular appearance in electron micrographs due to ribosomes that are attached to the cytoplasm side of the enclosing membranes. They are thus called rough endoplasmic reticulum. Others are devoid of ribosomes and are called smooth endoplasmic reticulum. Polypeptides can be identified in the channels of the rough endoplasmic reticulum. The function of the endoplasmic reticulum is the segregation of newly synthesized products and their further processing and intracellular transport. See also golgi apparatus. |
