Prokaryotes are unicellular organisms that lack organelles surrounded by what?

• Correct Answer: membranes
• tissues
• particles
• cells

Explanation: The Prokaryotic Cell Recall that prokaryotes (Figure 13.5) are unicellular organisms that lack organelles surrounded by membranes. Therefore, they do not have a nucleus but instead have a single chromosome—a piece of circular DNA located in an area of the cell called the nucleoid. Most prokaryotes have a cell wall lying outside the plasma membrane. The composition of the cell wall differs significantly between the domains Bacteria and Archaea (and their cell walls also differ from the eukaryotic cell walls found in plants and fungi. ) The cell wall functions as a protective layer and is responsible for the organism’s shape. Some other structures are present in some prokaryotic species, but not in others. For example, the capsule found in some species enables the organism to attach to surfaces and protects it from dehydration. Some species may also have flagella (singular, flagellum) used for locomotion, and pili (singular, pilus) used for attachment to surfaces and to other bacteria for conjugation. Plasmids, which consist of small, circular pieces of DNA outside of the main chromosome, are also present in many species of bacteria.

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