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Incoming links: Rough endoplasmic reticulum
Endoplasmic reticulum Created 2026-10-14 Updated 2026-10-18
The endoplasmic reticulum is a membrane-enclosed network of tubules and flattened sacs in a typical eukaryotic biological cell. Its continuous boundary encloses the ER lumen, separate from the cytosol, and connects with the outer nuclear envelope. Rough endoplasmic reticulum and smooth endoplasmic reticulum are regions of this network.[ref]
The Endoplasmic Reticulum. The Cell: A Molecular Approach, 2nd edition by Geoffrey M. Cooper; The Endoplasmic Reticulum, opening paragraph and Figure 9.1: continuous membrane and nuclear-envelope connection
One endoplasmic reticulum network with rough and smooth regions
. Original conceptual cross-section: blue interiors connect, while attached ribosomes distinguish rough regions. Shapes and dimensions are illustrative, not measured fluorescence or electron microscopy. Details.
Microsome 2026-10-18
A microsome is a closed lipid bilayer compartment produced during disruption of a biological tissue; rough endoplasmic reticulum-derived microsomes provide a sealed compartment for protein targeting experiments.
In 1967, James D. Jamieson and George E. Palade incubated guinea pig pancreas slices, following a three-minute pulse of tritium-labeled leucine with excess unlabeled leucine. This pulse-chase analysis marked newly made proteins while reducing subsequent incorporation. Fixed, Epon-embedded thin sections were mounted on coated grids, covered with Ilford L-4 photographic emulsion, developed and stained for electron microscopy. Autoradiography located photographic grains relative to pancreatic acinar cell structures.[ref]
Intracellular Transport of Secretory Proteins in the Pancreatic Exocrine Cell. II. Transport to Condensing Vacuoles and Zymogen Granules by James D. Jamieson and George E. Palade. Jamieson and Palade, Intracellular Transport of Secretory Proteins in the Pancreatic Exocrine Cell. II. Transport to Condensing Vacuoles and Zymogen Granules (1967), p. 598 Methods; Figure 10: three-minute pulse
Pulse-end samples provided a temporal reference: label lay mainly over rough endoplasmic reticulum; later samples shifted toward peripheral Golgi apparatus elements, condensing vacuoles and secretory granules. As a contamination check, isolated granule pellets were also examined by autoradiography: early pellet labeling chiefly marked condensing vacuoles. Grids from the compared pellet samples were coated together to control photographic processing. This supported transport of a previously labeled cohort rather than separate synthesis at each location. Fixed samples did not track individual proteins; localization was finite, and labeling was not absolutely exclusive to secretory cargo. The result concerns this preparation, not every protein in every biological cell.[ref]
Intracellular Transport of Secretory Proteins in the Pancreatic Exocrine Cell. II. Transport to Condensing Vacuoles and Zymogen Granules by James D. Jamieson and George E. Palade. pp. 603–606 and Figures 10–13: changing localization; pp. 610–611 and Figures 14–15, Table III: pellet check and matched emulsion processing; p. 611 General Premises: nonexportable-protein labeling
Rough endoplasmic reticulum 2026-10-18
Rough endoplasmic reticulum bears attached ribosomes on its cytosol surface. In a common mammalian route, protein targeting delivers a nascent chain into the ER lumen during biological translation. Other proteins enter the membrane. Free and attached ribosomes share the same basic machinery; targeting depends on their cargo.[ref]
The Endoplasmic Reticulum. Molecular Biology of the Cell, 4th edition by Bruce Alberts and others; Membrane-bound Ribosomes Define the Rough ER, Figures 12-36 and 12-37; Translocation Across the ER Membrane Does Not Always Require Ongoing Polypeptide Chain Elongation