eukaryote science definition

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.