Prokaryotic and Eukaryotic cell

Cells are broadly divided into prokaryotic cells and eukaryotic cells, according to whether their genetic materials are enclosed by a nuclear envelope or not.

Prokaryotic cells:

  • Prokaryotic (pro-primitive, karyon-nucleus) cells are the most primitive cells. They do not contain a definite nucleus
  • They are comparatively smaller.
  • The cells have very simple organization.
  • Cell organelles are absent.
  • The chromatin bodies remain scattered inside the cytoplasm. Such a type of nucleus without a nuclear membrane is called a nucleoid.
  • eg. Bacteria, Blue-green algae, Mycoplasma, PPLO (Pleuro Pneumonia Like Organisms), etc.

Eukaryotic cells:

  • These are believed to have evolved from prokaryotes.
  • Eukaryotic cells are larger than the prokaryotes.
  • They show better structural organization and increased functional efficiency than prokaryotes
  • Membrane bound cell organelles are present.
  • They contain a definite nucleus.
  • The chromatin bodies are enclosed by a nuclear membrane.


  • The prokaryotes are single celled very small organisms measuring usually less than a micrometer (um) and generally not bigger than 3 mm.
  • A definite nucleus and many membranous structures are absent.

Internal Structure

  • Prokaryotes have a cell wall surrounding the cell membrane (except in mycoplasma). The fluid matrix filling the cell is the cytoplasm.
  • There is no well-defined nucleus. The genetic material is basically naked, without a nuclear membrane. It is called a nucleoid.
  • In addition to the genomic DNA, many bacteria have small circular DNA outside the genomic DNA, called plasmids.
  • A specialized differentiated form of cell membrane called mesosome is the characteristic of prokaryotes. They are essentially infoldings of cell membrane.

Related image

Beginning from the outermost structure and moving inward, prokaryotes (eg a bacterial cell) have some or all of the following structures

  • Cell envelope (and modifications)
  • Cytoplasm & its components.
  • Nucleoid & other genetic materials.


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