Eukaryotes are distinguished by which structural feature?

Eukaryotes are distinguished by the presence of membrane-bound organelles, which are specialized structures within the cell that perform distinct functions. This feature is crucial to eukaryotic cells, allowing them to compartmentalize various biochemical processes, thus enhancing efficiency and regulation. Organelles such as the nucleus, mitochondria, endoplasmic reticulum, and Golgi apparatus all exemplify this organizational complexity. The membrane-bound nature of these organelles means they are enclosed by lipid bilayers, creating distinct internal environments that are vital for their specific functions.

While eukaryotes do possess a plasma membrane, DNA, and may have pili and flagella, these features are not exclusive to them. Prokaryotic cells also have plasma membranes and DNA, and some possess pili and flagella. The defining characteristic that sets eukaryotes apart from prokaryotes is indeed the presence of membrane-bound organelles, marking them as a more complex form of life.