endoplasmic reticulum n a system of interconnected vesicular and lamellar cytoplasmic membranes that functions esp. in the transport of materials within the cell and that is studded with ribosomes in some places see ROUGH ENDOPLASMIC RETICULUM
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a system of membranes present in the cytoplasm of cells. ER is described as rough when it has ribosome attached to its surface and smooth when ribosomes are absent. It is the site of manufacture of proteins and lipids and is concerned with the transport of these products within the cell (see also Golgi apparatus).
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(ER) an organelle of all eukaryotic cells, consisting of an interconnecting network of tubules, flat saccules (cisternae), and vesicles extending from the nuclear envelope to the cell surface, and specialized for protein processing and lipid synthesis; there are three specialized regions: the rough endoplasmic reticulum, smooth endoplasmic reticulum, and transitional endoplasmic reticulum, (qq.v.). See Plate 12.Medical dictionary. 2011.