Which one of the following structures is not present 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. In these cells, the genetic material is not enclosed within a nuclear envelope but is located in an irregularly shaped region called the nucleoid.

• Cell Wall: Most prokaryotes possess a cell wall (e.g., made of peptidoglycan in bacteria) for protection and structural integrity.
• Ribosomes: These are essential for protein synthesis and are present in both prokaryotic (70S) and eukaryotic (80S) cells.
• Plasma Membrane: This is a universal component of all living cells, acting as a selective barrier for the movement of substances.

Since prokaryotes lack a defined, membrane-enclosed nucleus, Option C is the correct answer.