Which statement correctly distinguishes prokaryotic cells from eukaryotic cells?

• A. They have a nucleus surrounded by a membrane.
• B. They lack a nucleus and membrane-bound organelles.
• C. They contain chloroplasts for photosynthesis.
• D. They require a nucleus for DNA transcription.

Answer: (B)

Prokaryotic versus eukaryotic cells differ in cellular organization: prokaryotes lack a defined nucleus and membrane-bound organelles, while eukaryotes have a true nucleus and many internal membranes. This distinction is the simplest and most consistent way to tell them apart. In prokaryotic cells, DNA resides in a nucleoid region not enclosed by a membrane, and there are no mitochondria, chloroplasts, or other membrane-bound compartments. Eukaryotic cells, on the other hand, contain a nucleus and various organelles separated by membranes, enabling compartmentalized functions like transcription in the nucleus and processes inside organelles. Therefore, saying that prokaryotic cells lack a nucleus and membrane-bound organelles captures the key difference. The other statements describe features typical of eukaryotes or not universal to prokaryotes (for example, having a nucleus, chloroplasts for photosynthesis, or nucleus-dependent transcription), so they don’t distinguish prokaryotes as reliably.