Biology
Diffusion
movement of molecules from a region of high concentration to a region of low concentration
passive process
does NOT need energy to occur
osmosis
movement of water molecules from a region of high water concentration to a region of low water concentration across a semi-permeable membrane
selectively permeable membrane
allows some but not all molecules to pass through the membrane
Isotonic
water moves in and out of cell at the same rate
Hypotonic (animal cell)
external environemnt less concentrated than the cytoplasm. Water enters the cell, it expands. May burst and die as there's no cell wall to contain the water
Hypertonic (animal cell)
External environmet is more concentrated than the cytoplasm , water leaves the cell by osmosis. The cell shrivels up, looses its shape and may die.
less concentrated
more water, less salt
more concentrated
less water, more salt
Hypotonic (plant cell)
Water moves into vacuole and cytoplasm, they swell and the cell membrane pushes againts cell wall. Cell wall is rigid and prevents thr cell bursting. Cell becomes turgid
Hypertonic (plant cell)
Water moves out of the cell (osmosis), it looses turgidity, cytoplasm shrinks and the cell membrane pulls away from cell wall. Cell is plasmolysised and plant begins to wilt.
plasmolysis
shrimkage of plant cell from cell wall due to loss of water by osmosis
material that acts as semi-permeable membrane in experiement.
Visking tubing
what two solutions are added to the visking tubing?
tube 1: sucrase solution
tube 2: distilled water