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Definition

noun, plural: organelles

A membrane-bound compartment or structure in a cell that performs a special function.

Supplement

A eukaryotic cell contains many organelles, for example, the nucleus, endoplasmic reticulum, golgi apparatus, mitochondria, and chloroplast (plastid). However, not all these organelles are found in only one cell or in an organism. The chloroplast, for instance, is abundant in plant cells but not in animal cells.

Prokaryotes, which were believed to have no organelles, have been recently described to possess “organelles”. Examples are carboxysome (a protein-shell compartment for carbon fixation in some bacteria), chlorosome (a light harvesting complex in green sulfur bacteria), magnetosome (found in magnetotactic bacteria), and thylakoid (in some cyanobacteria).

Word origin: New Latin organella, diminutive of Medieval Latin organum, organ of the body, from Latin, implement, tool

See also: nucleus, GERL.