eukaryote eu·kar·y·ote or eu·car·y·ote (yōō-kār'ē-ōt, -ē-ət)
A single-celled or multicellular organism whose cells contain a distinct membrane-bound nucleus.
An organism whose cells contain a nucleus surrounded by a membrane and whose DNA is bound together by proteins (histones) into chromosomes. The cells of eukaryotes also contain an endoplasmic reticulum and numerous specialized organelles not present in prokaryotes, especially mitochondria, Golgi bodies, and lysosomes. The organelles are enclosed in a three-part membrane (called a unit membrane) consisting of a lipid layer sandwiched between two protein layers. All organisms except for bacteria and archaea are eukaryotes. Compare prokaryote.
An organism whose cells contain a nucleus. All multicelled organisms are eukaryotes, as is one superkingdom of single-celled organisms. Eukaryotes also have organelles enclosed by membranes. (Compare prokaryote.)
Note: Eukaryotes evolved in a process in which one early prokaryote consumed another, forming a more complex structure.
Note: The word eukaryote comes from the Greek for “true nucleus.”