BaSIC STRuCTuRE aNd fuNCTION Of CEllS
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of external signals, including hormones and other ligands, and sites for abundant proteins; SER is abundant in steroid-producing cells and
the recognition and attachment of other cells. Internally, plasma mem- muscle cells. A variant of the endoplasmic reticulum in muscle cells is
branes can act as points of attachment for intracellular structures, in the sarcoplasmic reticulum, involved in calcium storage and release for
particular those concerned with cell motility and other cytoskeletal muscle contraction. For further reading on the endoplasmic reticulum,
functions. Cell membranes are synthesized by the rough endoplasmic see Bravo et al (2013).
reticulum in conjunction with the Golgi apparatus.
Smooth endoplasmic reticulum
Cell coat (glycocalyx)
The smooth endoplasmic reticulum (see Fig. 1.4) is associated with
The external surface of a plasma membrane differs structurally from carbohydrate metabolism and many other metabolic processes, includ-
internal membranes in that it possesses an external, fuzzy, carbohydrate- ing detoxification and synthesis of lipids, cholesterol and steroids. The