Which of the following describes the basic characteristic of eukaryotic cells?

• A. Lacks a nucleus
• B. Has no organelles
• C. Is always unicellular
• D. Has a nucleus and membrane-bound organelles

Answer: (D)

Eukaryotic cells are defined by compartmentalization: they have a true nucleus enclosed by a membrane and a suite of membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus. This structure allows DNA to be housed in the nucleus and separates different cellular processes into distinct environments, making complex regulation and specialized functions possible. In contrast, cells without a nucleus and without membrane-bound organelles (the typical description of prokaryotes) lack this level of internal division. Eukaryotic cells can be either single-celled or part of multicellular organisms, so the presence of a nucleus and membrane-bound organelles is the hallmark feature.