Sunday, 29 June 2014

The Fundamental Unit of Life – Diffusion & Osmosis (Part -2)

Diffusion

  • Diffusion is defined as the movement of particles from a region of high concentration to a region of low concentration.
Diffusion- Cell

Osmosis

  • Osmosis is defined as the passage of water from a region of high water concentration to a region of low concentration through a Semi-permeable membrane.
  • Ex-osmosis : The passage(exit) of water from inside to outside of a cell. E.g.:- Tender Mango Shrinks when put in Salt Solution.
  • End-osmosis : The passage (entry) of water from outside to inside of a cell. E.g.:- Raisins swells when dropped in Water.
Hyper-tonic Solution  (EXOSMOSIS)
Exosmosis
  • A solution that has Less  concentration of water as compared to the cell placed in it.
  • The water from the cells exits to the solution, due to Ex-osmosisand therefore thecell shrinks.
Hypo-tonic Solution (ENDOSMOSIS)
  • A solution that has More concentration of water as compared to the cell placed in it.
  • The water enters the cell from the solution, due to End-osmosis,  and therefore the cell swells.
Isotonic Solution (No net Osmosis)
  • A solution that has Same concentration of water as compared to the cell placed in it.
  • Since there is not net movement of water (osmosis) across the cell, no change in shape is observed.
Plasmolysis (HYPERTONIC)
  • The detachment of cell membrane of the plant cell from the cell wall when put in Hypertonic solution is known as Plasmolysis.
  • A Cell that has undergone Plasmolysis is called Plasmolysed Cell.
  • Plasmolysis happens only in Plant Cells (i.e. cells having cell wall).
Turger Pressure : The pressure excreted by the cell membrane on to the cell wall, when it wants to take in water is known as Turger Pressure.
Wall Pressure : The pressure excreted  by  the cell wall on to the cell membrane is known as Wall Pressure.
Endocytosis: The process by which the cell engulfs food and other materials from its external surroundings is called endocytosis.

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