Microbiology, 2021

3.3 • Unique Characteristics of Prokaryotic Cells 85
• What kinds of infectious agents are known to cause pneumonia?
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Figure 3.11
(credit “swan-neck flask”: modification of work by Wellcome Images)
3.3 Unique Characteristics of Prokaryotic Cells
Learning Objectives
By the end of this section, you will be able to:
• Explain the distinguishing characteristics of prokaryotic cells
• Describe common cell morphologies and cellular arrangements typical of prokaryotic cells and explain how
cells maintain their morphology
• Describe internal and external structures of prokaryotic cells in terms of their physical structure, chemical
structure, and function
• Compare the distinguishing characteristics of bacterial and archaeal cells
Cell theory states that the cell is the fundamental unit of life. However, cells vary significantly in size, shape,
structure, and function. At the simplest level of construction, all cells possess a few fundamental components.
These include cytoplasm (a gel-like substance composed of water and dissolved chemicals needed for growth),
which is contained within a plasma membrane (also called a cell membrane or cytoplasmic membrane); one
or more chromosomes, which contain the genetic blueprints of the cell; and ribosomes, organelles used for
the production of proteins.