Prokaryotic vs. Eukaryotic Cells:
A typical prokaryotic cell (in this case, from a bacterium).
As discussed in the previous chapter, bacteria and archaeans are
prokaryotes. All other organisms are
eukaryotes. The cells of prokaryotes are almost always much smaller than are those of eukaryotes, and they’re much simpler. As you can see in the illustration above, the genetic material of a prokaryotic cell is more or less scattered throughout the cell, and there are few specialized substructures (
organelles) within the cell.
A typical eukaryotic cell (in this case, from an animal).
Compared to a prokaryotic cell, a eukaryotic cell is almost always much larger. It is also far more complex. Various smaller structures called
organelles perform specialized tasks within a eukaryotic cell. Typically, the largest of these organelles is the
nucleus, where the cell’s DNA is found.
In some ways, eukaryotic cells are much more efficient than are prokaryotic cells. Their relative inefficiency may be one reason why almost all prokaryotes are single-celled (
unicellular) organisms. In contrast, a great many eukaryotic organisms are
multicellular, having bodies that are made up of many cells working together in a tightly-coordinated fashion.