A comparison of the bacterial and eukaryotic cells in demonstrates that there are many fundamental differences between these cells.
These differences are also observed between archaeal and eukaryotic cells, because archaea are similar to bacteria at the gross structural level.
Eukaryotic cells have a membrane-enclosed nucleus.
In contrast, bacterial and archaeal cells lack a true, membrane-delimited nucleus.
Most bacteria and archaea are smaller than eukaryotic cells, often about the size of eukaryotic mitochondria and chloroplasts.
Many other major distinctions between these groups exist.
that bacterial and archaeal cells are much simpler structurally.
In particular, an extensive and diverse col lection of membrane-delimited organelles is missing.
Further more, bacterial and archaeal cells are functionally simpler in several ways.
They lack mitosis and meiosis, and have a simpler genetic organization.
Many complex eukaryotic processes are ab sent in bacteria and archaea: endocytosis, intracellular digestion, directed cytoplasmic streaming, and ameboid movement are just a few.
Despite the many significant differences, all cells are re markably similar on the biochemical level, as we discuss in succeeding chapters.
With a few exceptions, the genetic code is the same in all, as is the way in which the genetic informa tion in DNA is expressed.
The principles underlying meta bolic processes and many important metabolic pathways are identical.
Thus beneath the profound structural and func tional differences between bacterial, archaeal, and eukaryotic cells, there is an even more fundamental unity: a molecular unity that is basic to all known life processes.
Retrieve, Infer, Apply
1. Outline the major differences between bacterial, archaeal, and eukaryotic cells. How are they similar?
2. What characteristics make members of Archaea more like eukaryotes? What features make them more like bacteria?
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