endomembrane system

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endomembrane system The hypothetical concept that the membranes of many apparently discrete cell structures are part of an interrelated system. It proposes that new membrane is constantly being made in the endoplasmic reticulum and transported, in the form of vesicles, to the various organelles. Hence, the membranes of the nucleus, endoplasmic reticulum, Golgi apparatus (or dictyosomes), plasma membrane, tonoplast, and outer (but not inner) membranes of the mitochondria and chloroplasts form a functional continuum within the cell.