Cell : The Unit of Life

Structure of prokaryotic cell

  • Prokaryotic cells are small in size (1-10μm).
  • They are unicellular organisms eg. bacteria, blue green algae, mycoplasma and PPLO (pleuro pnemonia like organism)
  • All prokaryotes have a cell wall (composed of peptidoglycans) surrounding the cell membrane. It also contains the fluid filled matrix named cytoplasm.
  • The main difference between prokaryote and eukaryote is that, the genetic material present in prokaryotes is naked circular DNA, not enclosed by nuclear envelope.
  • Many bacteria have small circular DNA along with genomic DNA
  • On the plasma membrane, some circular coiled bodies called mesosomes are present which contain respiratory enzymes like oxidases and dehydrogenase and help in respiration.
  • The cell envelope consist of tightly bound three layered structure i.e, the outermost glycocalyx followed by the cell wall and the cell membrane.
  • Gram positive bacteria (eg: streptococcus, staphylococcus, Bacillus, Mycobacterium, streptomyces etc) respond to gram staining, others that do not are called gram negative (eg: salmonella, pseudomonas, E.Coli, Rhizobium, Helicobacter etc).
  • The plasma membrane present in prokaryotes are similar to that of eukaryotes which is semipermeable in nature and interact with outersurface.
  • Bacterial cells may be motile or non motile. Motile bacteria has flagella which is composed of three parts- filament, hook and basal body.
  • The cytoplasm present in prokaryotes is granular due to the presence of large number of ribosomes (70s).
  • Reserve material stoned in the form of inclusion bodies which is present in cytoplasm. (Eg:- Phosphate granules, glycogen granules).
  • Cell division of prokaryotes are mostly amirotic.
  • To remember gram -Ve & gram +Ve bacteria → LONG PPT
    L - Lipopolysaccharide   P - Positive
    O - Outermembrane      P - peptidoglycan (Thick)
    N - Negative                 T - Teichoic acid

View this video for the topic from 8:52 to 27:53


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