The irregular network of unit membranes, visible only by electron microscopy, that occurs in the cytoplasm of many eukaryotic cells. The membranes form a complex meshwork of tubular channels, which are often expanded into slitlike cavities called cisternae. The ER takes two forms, rough (or granular), with ribosomes adhering to the outer surface, and smooth (with no ribosomes attached) [goid 5783] [evidence IEA]; Penetrating at least one phospholipid bilayer of a membrane. May also refer to the state of being buried in the bilayer with no exposure outside the bilayer. When used to describe a protein, indicates that all or part of the peptide sequence is embedded in the membrane [goid 16021] [evidence IEA]; The irregular network of unit membranes, visible only by electron microscopy, that occurs in the cytoplasm of many eukaryotic cells. The membranes form a complex meshwork of tubular channels, which are often expanded into slitlike cavities called cisternae. The ER takes two forms, rough (or granular), with ribosomes adhering to the outer surface, and smooth (with no ribosomes attached) [goid 5783] [evidence IEA]; A translocation complex that constitutes the specific site of protein translocation across the endoplasmic reticulum, which involves the signal recognition particle receptor. Composed of a heterotetramer of alpha, beta, gamma and delta subunits (translocon-associated proteins or TRAPs). In yeast it is a heterotrimeric complex consisting of Sec61p, Sbh1p, and Sss1p. The Sec61 complex functions in cotranslational and posttranslational translocation events [goid 5784] [pmid 9286695] [evidence NAS]; A translocation complex that constitutes the specific site of protein translocation across the endoplasmic reticulum, which involves the signal recognition particle receptor. Composed of a heterotetramer of alpha, beta, gamma and delta subunits (translocon-associated proteins or TRAPs). In yeast it is a heterotrimeric complex consisting of Sec61p, Sbh1p, and Sss1p. The Sec61 complex functions in cotranslational and posttranslational translocation events [goid 5784] [pmid 7492314] [evidence NAS]; The lipid bilayer surrounding the endoplasmic reticulum [goid 5789] [evidence IEA]; Double layer of lipid molecules that encloses all cells, and, in eukaryotes, many organelles; may be a single or double lipid bilayer; also includes associated proteins [goid 16020] [evidence IEA]; Penetrating at least one phospholipid bilayer of a membrane. May also refer to the state of being buried in the bilayer with no exposure outside the bilayer. When used to describe a protein, indicates that all or part of the peptide sequence is embedded in the membrane [goid 16021] [evidence IEA]