Which statement best characterizes prokaryotic cells?

• A. They are enclosed within a cell wall and lack a defined nucleus and membrane-bound organelles.
• B. They contain a defined nucleus and membrane-bound organelles.
• C. They are always larger than eukaryotic cells.
• D. They have chloroplasts for photosynthesis.

Answer: (B)

Prokaryotic cells are simple in organization: they do not have a defined nucleus or any membrane-bound organelles. Their DNA floats in a nucleoid region within the cytoplasm, and all essential functions occur in a relatively unsegmented interior. They typically have a cell wall and a plasma membrane, plus ribosomes, and may have structures like flagella or pili, but nothing enclosed by a separate membrane-bound compartment like a mitochondrion or Golgi apparatus.

That lack of a nucleus and membrane-bound organelles is what sets prokaryotes apart from eukaryotic cells, which do have a defined nucleus and internal compartments. Chloroplasts, which are used for photosynthesis in many plant and algal cells, are organelles found in eukaryotes and are not present in prokaryotes. Prokaryotes can perform photosynthesis via specialized internal membranes, but they don’t contain chloroplasts.