Prokaryotic cells share basic features, including the cell membrane and a region called the nucleoid. The rest of the material enclosed by the cell membrane, including the ribosomes, is called the cytoplasm. Other features, such as cell walls, internal membranes, and flagella, are present in some but not all prokaryotes.
learning outcomes
You should be able to:
Describe the major features of a prokaryotic cell.
Identify specialized features found in some prokaryotic cells.
What are the structure and function of the following specialized prokaryotic cell features: cell wall, capsule, and flagellum?
The cell wall is composed of a large complex of polysaccharides and peptides. It supports the cell and gives it shape. The capsule is a slimy polysaccharide layer that encloses the cell walls of some prokaryotes and keep cells from drying out. It may be used to attach to other cells. The flagellum is composed of strands of a large protein called flagellin and is attached to the cell wall and membrane by a motor complex. It is used for cell movement.
What are the chemical compositions of the nucleoid and cytoplasm in a prokaryotic cell?
The nucleoid consists of DNA and proteins. Cytoplasm contains all the other small and large molecules for life, dissolved or suspended in water.
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As we have already noted, the prokaryotic cell is one of two types of cell recognized in cell biology. The other is the eukaryotic cell. Eukaryotic cells are more structurally and functionally complex than prokaryotic cells.