Which one of the following is NOT found in a prokaryotic cell ?

Prokaryotic cells (such as bacteria and archaea) are characterized by the absence of a membrane-bound nucleus and other membrane-bound organelles. The genetic material in a prokaryote is typically a single circular molecule of DNA located in a region called the nucleoid, which is not enclosed by a nuclear membrane.

• Cell wall: Most prokaryotes have a rigid cell wall (e.g., made of peptidoglycan in bacteria) that provides structural support.
• Ribosome: Prokaryotes contain 70S ribosomes, which are essential for protein synthesis.
• Plasmid DNA: Many prokaryotes contain small, circular, extrachromosomal DNA molecules called plasmids.

Therefore, the nuclear membrane is the structure specifically absent in prokaryotic cells but present in eukaryotic cells.