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In cell biology, an organelle is a specialized subunit within a cell that has a specific function. Individual organelles are usually separately enclosed within their own lipid bilayers. The name ''organelle'' comes from the idea that these structures are to cells what an organ is to the body (hence the name ''organelle,'' the suffix ''-elle'' being a diminutive). Organelles are identified by microscopy, and can also be purified by cell fractionation. There are many types of organelles, particularly in eukaryotic cells. While prokaryotes do not possess organelles ''per se'', some do contain protein-based microcompartments, which are thought to act as primitive organelles. == History and terminology == In biology ''organs'' are defined as confined functional units within an organism.〔 〕 The analogy of bodily organs to microscopic cellular substructures is obvious, as from even early works, authors of respective textbooks rarely elaborate on the distinction between the two. Credited as the first〔''Amer. Naturalist''. 23, 1889, p. 183: "It may possibly be of advantage to use the word organula here instead of organ, following a suggestion by Möbius. Functionally differentiated multicellular aggregates in multicellular forms or metazoa are in this sense organs, while, for functionally differentiated portions of unicellular organisms or for such differentiated portions of the unicellular germ-elements of metazoa, the diminutive organula is appropriate." Cited after: Oxford English Dictionary online, entry for "organelle".〕〔('Journal de l'anatomie et de la physiologie normales et pathologiques de l'homme et des animaux' at Google Books )〕 to use a diminutive of ''organ'' (i.e., little organ) for cellular structures was German zoologist Karl August Möbius (1884), who used the term ''organula'' (plural of ''organulum'', the diminutive of Latin ''organum'').〔 〕 In a footnote, which was published as a correction in the next issue of the journal, he justified his suggestion to call organs of unicellular organisms "organella" since they are only differently formed parts of one cell, in contrast to multicellular organs of multicellular organisms. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「organelle」の詳細全文を読む スポンサード リンク
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