Endoplasmic reticulum is a network of tubules, vesicles and sacs that are interconnected. They may serve specialized functions in the cell including protein synthesis, sequestration of calcium, production of steroids, storage and production of glycogen, and insertion of membrane proteins. The first part of this presentation will focus on rough endoplasmic reticulum, which gets its name from the presence of ribosomes on its surface.
The text reading for this discussion is Alberts et al, Molecular Biology of the Cell, third edition, Garland Publishing, 1994, pp 577-588 (Chapter 12) and pp 599-616.
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Rough endoplasmic reticulum bears the ribosomes during protein synthesis. The newly synthesized proteins are sequestered in sacs, called cisternae . The system then sends the proteins via small vesicles to the Golgi Complex , or, in the case of membrane proteins, it inserts them into the membrane. As shown in this diagram, rough endoplasmic reticulum may either be vesicular or tubular. Or it may consist of stacks of flattened cisternae (like sheets) that may have bridging areas connecting the individual sheets. The Ribosomes sit on the outer surfaces of the sacs (or cisternae). They resemble small beads sitting in rosettes or in a linear pattern.
Rough endoplasmic reticulum forms a branched reticulum that expands as the cell becomes more active in protein synthesis. Sometimes the reticulum branches out. Other times, the cisternae dilate and form large sacs that fill the cell. The above photograph, taken from your text, shows the reticulum delineated by immunolabeling for newly synthesized protein (labeled fluorescent blue in this photo).
For more information, contact:
Gwen Childs, Ph.D.,FAAA
Professor and Chair
Department of Neurobiology and Developmental Sciences
University of Arkansas for Medical Sciences
Little Rock, AR 72205
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