BI108 Chapter 5 Outline: Cells: The Working Units of Life
5.1—What Features Make Cells the Fundamental Units of Life?
• Cell size is limited by the surface are-to-volume ratio
• Microscopes reveal the features of cells
• The plasma membrane forms the outer surface of every cell
• Cells are classified as either prokaryotic or eukaryotic
The cell theory is a unifying principle in biology. Both prokaryotic and eukaryotic cells
are enclosed within a plasma membrane, but prokaryotic cells lack the membrane-
enclosed organelles that are found in eukaryotic cells.
5.2—What Features Characterize Prokaryotic Cells?
• Prokaryotic cells share certain features
• Specialized features are found in some prokaryotes
Prokaryotic cells share certain features, including the plasma membrane, the nucleoid,
and the cytoplasm, which consists of the liquid cytosol and insoluble filaments and
particles, including ribosomes. Other features, such as cell walls, internal membranes,
and flagella, are present in some, but not all.
5.3—What Features Characterize Eukaryotic Cells?
• Organelles can be studied by microscopy or isolated for chemical analysis
• Ribosomes are factories for protein synthesis
• The nucleus contains most of the genetic information
• The endomembrane sys