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An overview of cell

  •  A typical plant cell, has a distinct cell wall as its outer boundary and just within it is the cell membrane .
  • Cells that have membrane bound nuclei are called eukaryotic whereas cells that lack a membrane bound nucleus are prokaryotic .
  • in both prokaryotic and eukaryotic cells,  a semi- fluid matrix called cytoplasm occupies the volume of the cell.
  • The cytoplasm is the main arena of cellular activities in both the plant and animal cells. various chemical reactions occurs in it to keep the cell in the living state.,
  • Besides the nucleus, the eukaryotic cells have other membrane bound distinct structures called organelles like the endoplasmic reticulum (ER), the golgi complex, lysosomes, microbodies . the prokaryotic cells lack such membrane bound organelles.
  • Ribosomes are non-membrane bound organelles found in all cells - both eukaryotic as well as prokaryotic cells. Within the cell, ribosomes  are found not only in the cytoplasm but also within the two organelles chloroplast (in plants ) and mitocondria and on rough ER .

Animal cells contain another non-membrane bound organelle called centriole which helps in cells division.

SIZE :-

  • Cells differ greatly in size , shape and activities .
  •  Mycoplasma (smallest cells) ; only 0.3µm in length [PPLO (pleuro pneumonia like organism) ] is a type of mycoplasma having the size about 0.1µm .
  • Largest isolated single cell = egg of an ostrich .
  • Human red blood cell = 7.0µm in diameter .
  • Nerve cell = longest cell
Shape:-
       

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