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Class 11 th PROKARYOTIC CELL NEETIAIIMS/JIPMER -ANMOL SHARMA
Introduction Cells come in various shapes and sizes. .Based on the presence of a nucleus or membrane-bound organelles, cells are broadly classified as Prokaryotic cells or Eukaryotic cells. . Let's learn about each in more detail.
Classification In 1977, Carl Woese proposed divided prokaryotes in: . Bacteria and Archaea (originally Eubacteria and Archaebacteria) because of the major differences in the structure and genetics between the two groups of organisms. . Archaea were originally thought to be extremophiles, living only in inhospitable conditions such as extremes of temperature, pH, and radiation but have since been found in all types of habitats.
Prokaryotic Cell . Prokaryotic cells lack both, a well- defined nucleus and membrane- bound cell organelles. Examples of prokaryotes are blue- green algae, bacteria and mycoplasma.
Among prokaryotes, bacteria are the most common and multiply very fast. They are single-celled and range in size from 0.2 to 10 microns (about 10 times smaller than most plant and animal cells). Bacteria are found everywhere - in rocks, soil ocean water. Did you know that there are approximately 10 times more bacterial cells than human cells in the human body? Now, most of these bacteria are found in the digestive system where they help in digesting food
. Based on the shape, there are four types of bacteria: 1.Bacillus (rod-like) 2.Coccus (spherical) 3.Spirillum (Spiral) 4.Vibrio (Comma-shaped)
Components of a Prokaryotic Cell:- Cell Envelope Cytoplasm Mesosomes . Chromatophores Ribosomes Inclusion Bodies . Flagella Pili and Fimbriae(Reproduction) . Nucleoid DNA transfer