Function of plasma membrane (endocytosis, Pinocytosis, junctions)

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FUNCTIONS OF PLASMA MEMBRANE

    PART-2 

CONTINUING FROM PART-1 

b) Endocytosis- It is of two types:-

      I) Phagocytosis- It is editing phenomenon where large particle like bacteria dead cell debris etc. are engulfed in by vesicle formed by plasma membrane. The vesicle is called phagosome. 

                Example-macrophages,kupffer cells in liver ,reticular cell in spleen ,histocytes in connective tissue, monocytes and neutrophils.

       II) Pinocytosis- It is the non specific uptake of small droplets of extracellular fluid by pinosome. It is a cell drinking phenomenon.

2) plasma membrane separates Protoplasm from external environment.

3) plasma membrane protect cell from injury.

4) plasma membrane forms sheat of cilia and flagella.

5) plasma membrane forms various types of in folding like:

   I) Microvillus:- It increases the surface area for absorption of digested food in small intestine and solutes in nephron.

  II) Mesosomes:-  It is found in Gram Positive Bacteria to perform molecular respiration.

  III)Lamelasome:- It is structurally and functionally similar to mesosome and found in blue green algae.

  IV)Lomasome:- It is in folding of plasma membrane in fungi which help in diffusion of substances during cell wall formation.

6) various type of junctions:-

     I) Tight Junction:- At this junction adjacent cell get fused. A protein band binds plasma membrane. 

                       Example:-  It is found in blood capillaries, collecting tubules and brain cells.

      II) Gap junctions:- At this junction adjacent cells have protoplasmic connections through special proteins called connexions.

                           Example:- Cardiac muscle cells.

        III) Desmosomes:- At this junctions , adjacent membrane possess disc shaped thickening.The disc possess tonofibrils.

                 Example:- Stratified squamous epithelia.

        IV) Terminal bar:- It is same to desmosomes but lack tonofibrils.

             

                 Example:- Stratified squamous epithelia.

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