Definition
noun, plural: endomembranes
The membraneous components in a cell, i.e. nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, endosomes, vesicles, and the cell membrane, acting as a single functional and developmental unit
Supplement
The endomembrane refers to the membranous components within the eukaryotic cell. These membranous components include the membranes of nucleus (i.e. nuclear envelope), endoplasmic reticulum, Golgi apparatus, lysosomes, endosomes, vesicles, and the cell membrane. It does not include the membranes of mitochondria and/or chloroplasts. The membranes of the organelles included in the endomembrane system may be related through direct contact, e.g. the nuclear envelope being connected to the endoplasmic reticulum, and the latter to the Golgi apparatus, or by indirect contact, e.g. by the transfer of membrane segments as vesicles. In general, the endomembrane system is involved in the manufacturing and distributing cellular products. However, each of these organelles performs specific functions within the cell. For instance, the endoplasmic reticulum is involved in the synthesis of various biomolecules. The Golgi apparatus is involved in the packaging of biomolecules newly synthesized from the endoplasmic reticulum. The membranes of these organelles may also vary in structure. For instance, some of them consist of two lipid bilayers (e.g. nuclear envelope) while others are comprised of only one (e.g. lysosome). Nevertheless, their membranes share the same fundamental structure in a way that they are a lipid bilayer with proteins attached or traversing the lipid bilayer.
Word origin: Greek endo- (within) + membrane
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