effects of osmosis on plants+ animals

• hydrostatic pressure 


  = the diffusion of water into a solution leads to an increase in volume of this solution. If the solution is in a closed system, such as a cell, this results in an increase in pressure.
• animal cells

  = if animal cell is placed in solution with a higher water potential than the cytoplasm, water will move into the cell by osmosis, increasing the hydrostatic pressure inside the cell.

  • all cells have thin cell-surface membranes and no cell walls.
  • The cell-surface membrane can't stretch much and can't withstand increased pressure. It will break and the cell will burst= cytolysis.
• animal cells 


  = if cell placed in a solution that has lower water potential than the cytoplasm it will lose water to the solution by osmosis.

  • will cause a reduction in the volume of the cell and the cell-surface membrane to 'pucker'= crenation.
• to prevent either cytolysis or crenation, animals have control mechanisms to make sure their cells are continuously surrounded by aqueous solutions with an equal water potential.
• Plant cells

  = unable to control the water potential of the fluid around them.

  • plants have strong cellulose walls surrounding cells-surface membranes.
  • when water enters by osmosis the increased hydrostatic pressure pushes the membrane against the rigid cell walls= turgor.
  • as the turgor pressure increases it resists the entry of further water and cell is said to be turgid.
• plant cells

  = placed in solution with lower water potential than their own, water is lost from the cells.

  • leads to a reduction in the volume of cytoplasm , which then pulls the cell-surface membrane away from the cell wall- cell is plasmolysed.