Prokaryotic cells: (Pro = Before; Eukaryotic = nucleus)

Examples: Bacteria & Blue-green Algae

They are "primitive" cells which lack membrane-bound organelles (no organized nucleus, vacuoles, etc.)

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PROKARYOTE CELL STRUCTURE

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2. Cell wall: Rigid to semirigid wall surrounding plasma membrane. Contains pores to allow passage of materials in & out. The cell wall supports cell and provides shape.

3. Plasmid: Small circular pieces of naked DNA in addition to main chromosome of prokaryote cells.

4. Nucleoid: Region of prokaryote cytoplasm where main chromosome and plasmid are found. Naked DNA - DNA is not bound to proteins (like histones) to reduce the amount of space they take up.

5. Mesosome: Internal membrane connected to the cell surface membrane. It increases the area available to make ATP (cell energy). It may also aid the replication of DNA and cell division.

6. Cytoplasm: Contains enzymes for catalyzing chemical reactions of metabolism. Contains ribosomes and naked DNA.

7. Ribosome: Sites of protein synthesis (scattered throughout cytoplasm rather than in rough ER).

8. Flagellum: One to many threadlike, motile structures (locomotion).

9. Slime capsule: Layer of thick, jellylike polysaccharides surrounding some prokaryote cells to aid in protection.

Prokaryotic cells divide by binary fission: They double their chromosome number (1--->2) and then split in half.