What is the main difference between prokaryotic and eukaryotic cells?

• A. The nucleus and other membrane-bound organelles are present only in eukaryotic cells.
• B. Prokaryotic cells have a nucleus.
• C. Eukaryotic cells lack organelles.
• D. All cells have mitochondria.

Answer: (A)

The main difference is how cellular organization is arranged: eukaryotic cells have a nucleus enclosed by membranes and contain internal membrane-bound organelles, while prokaryotic cells do not have a true nucleus or internal membrane-bound compartments. In eukaryotes, DNA sits inside the nuclear envelope, and organelles such as mitochondria and the endoplasmic reticulum carry out specialized functions. Prokaryotes store their DNA in a nucleoid region without a surrounding membrane and lack the internal membranes that define eukaryotic cells. This fundamental organizational difference is why the statement about the nucleus and membrane-bound organelles being present only in eukaryotic cells best captures the contrast. The other ideas don’t fit because prokaryotes do not have a nucleus, eukaryotes do have organelles, and mitochondria are not present in all cells (they’re characteristic of eukaryotes).