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  2. Domain (biology) - Wikipedia

    en.wikipedia.org/wiki/Domain_(biology)

    According to the domain system, the tree of life consists of either three domains, Archaea, Bacteria, and Eukarya, [1] or two domains, Archaea and Bacteria, with Eukarya included in Archaea. [ 3 ] [ 4 ] In the three-domain model , the first two are prokaryotes , single-celled microorganisms without a membrane-bound nucleus .

  3. Prokaryote - Wikipedia

    en.wikipedia.org/wiki/Prokaryote

    Eukaryotic cells are some 10,000 times larger than prokaryotic cells by volume, have their DNA organised in a nucleus, and contain membrane-bound organelles. The division between prokaryotes and eukaryotes has been considered the most important distinction or difference among organisms.

  4. Two-domain system - Wikipedia

    en.wikipedia.org/wiki/Two-domain_system

    The tree of life. Two domains of life are Bacteria (top branches) and Archaea (bottom branches, including eukaryotes). The two-domain system is a biological classification by which all organisms in the tree of life are classified into two domains, Bacteria and Archaea.

  5. Cell (biology) - Wikipedia

    en.wikipedia.org/wiki/Cell_(biology)

    Cells are broadly categorized into two types: eukaryotic cells, which possess a nucleus, and prokaryotic cells, which lack a nucleus but have a nucleoid region. Prokaryotes are single-celled organisms such as bacteria, whereas eukaryotes can be either single-celled, such as amoebae, or multicellular, such as some algae, plants, animals, and fungi.

  6. Marine prokaryotes - Wikipedia

    en.wikipedia.org/wiki/Marine_prokaryotes

    Eukaryotes are organisms whose cells have a nucleus enclosed within membranes, whereas prokaryotes are the organisms that do not have a nucleus enclosed within a membrane. [ 1 ] [ 2 ] [ 3 ] The three-domain system of classifying life adds another division: the prokaryotes are divided into two domains of life, the microscopic bacteria and the ...

  7. S-layer - Wikipedia

    en.wikipedia.org/wiki/S-layer

    An S-layer (surface layer) is a part of the cell envelope found in almost all archaea, as well as in many types of bacteria. [1] [2] The S-layers of both archaea and bacteria consists of a monomolecular layer composed of only one (or, in a few cases, two) identical proteins or glycoproteins. [3]

  8. Periplasm - Wikipedia

    en.wikipedia.org/wiki/Periplasm

    For the bacterial (prokaryotic) cells that are bounded by a single cell membrane the term "monoderm bacteria" or "monoderm prokaryotes" has been proposed. [ 4 ] [ 8 ] In contrast to gram-positive bacteria, all archetypical Gram-negative bacteria are bounded by a cytoplasmic membrane as well as an outer cell membrane; they contain only a thin ...

  9. Three-domain system - Wikipedia

    en.wikipedia.org/wiki/Three-domain_system

    The three-domain system adds a level of classification (the domains) "above" the kingdoms present in the previously used five- or six-kingdom systems.This classification system recognizes the fundamental divide between the two prokaryotic groups, insofar as Archaea appear to be more closely related to eukaryotes than they are to other prokaryotes – bacteria-like organisms with no cell nucleus.