General Characters of Plasma membrane


General Characters of Plasma membrane

Plasma Membrane – General Feature & structure

Plasma Membrane

  • Studied – By overton
  • The protoplasm of all cells is surrounded by one living cell membrane. It is also called plasma membrane or plasmalemma.
  • it was discovered by Swedish Botanist Carl Nagcli and C. Cramer in 1855.
  • J.Q. Plowe (1931) Give the name – Plasmalema.
  • Robertson – Unit Membrane
  • It is the part of cytoplasm.
  •  molecules of cytoplasm organised in a special pattern at outer surface of cytoplasm form plasma membrane.
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General Characters of Plasma membrane

  • It is 60A⁰ to 105A⁰ thick.
  • It is made up of Lipid and protein.
  • The lipid layer is bipolar, its internal part is called tail and outer part is called head. The tail is hydrophobic and the head is hydrophilic part of lipid.
  • The outer protein of plasma membrane can be easily removed but inner protein can not be removed.
  • It can be synthesised artificially.
  • It controls the molecule from outside of the cell.
  • It maintains ionic concentration inside and outside the cell. Thus it controls interaction among different cells. 
  • It receives signals from outer environment and acts as communicator 
  • In plants plasma membrane lies in between cell wall and cytoplasm whereas in animal cell it is the outermost covering  of the cell.

Ultra Structure of Plasma Membrane

Three layered structure of plasma membrane  seen under electron microscope. 

(1) Outer dense layer – protein rich 20 A thick.

(2) Inner dense layer  protein rich 20A thick

(3) Middle layer -phospholipid layer 35A thick, yellow coloured lies in between outer and inner protein rich layers.In this Hydrophilic head is toward the outside and hydrophobic tail is toward the mid.

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