Which of the following structures is found in all prokaryotic cells?

• A. Chloroplast
• B. Cell membrane
• C. Nucleus
• D. Mitochondria

Answer: (B)

Verified step by step guidance

1. Understand the definition of prokaryotic cells: Prokaryotes are unicellular organisms that lack membrane-bound organelles such as a nucleus, mitochondria, and chloroplasts.
2. Recall the common structures present in all prokaryotic cells: These include the cell membrane, cytoplasm, ribosomes, and genetic material (usually a single circular DNA molecule).
3. Identify which structures from the options are membrane-bound organelles: Chloroplasts, nucleus, and mitochondria are all membrane-bound organelles found only in eukaryotic cells, not prokaryotes.
4. Recognize that the cell membrane is a universal structure found in all cells, including prokaryotes, serving as a protective barrier and regulating the movement of substances in and out of the cell.
5. Conclude that the correct answer is the cell membrane, as it is the only structure listed that is present in all prokaryotic cells.