Plasmolysis: Filament of Spirogyra in pond of water was placed on a glass slide. It was observed under low power of the microscope and the cells were found to be turgid. The pond water was absorbed using a filter paper. A drop of strong salt solution was added and was left for a few minutes. It was observed that the cell wall was leaving a gap 'copied from g i s t p o w e r . c o m free' between the cell wall and the plasma membrane, showing that exosmosis has occurred or the cells have been plasmolysed.
Osmosis using living materials:
(i) Obtain three cassava or yam tubers
(ii) Peel off the tubers with a knife
(iii) Scoop out a portion of the tubers with a knife
(iv) Prepare a concentrated solution of sugar solution
(v) Pour some amount of the sugar solution into the scooped parts of the tubers and note the levels of the solution in the tubers
(vi) Put one tuber in boiling water for about five minutes to kill the cells
(vii) Put the base of each tuber in petri dishes containing some amounts of water
(viii) Sugar solution is put in fresh cube A, one fresh cube B is filled with water and the boil cube C.
(i) Level of sugar solution in A has risen
(ii) Levels of solutions in B and C remained the same
(i) Water has been drawn by osmosis through the yam tissues in A into the sugar solution (higher concentration of solute, but lower concentration of water).
(ii) There is no rise in B because the concentration of the water in yam is the same as the concentration of the water in the petri 'copied from g i s t p o w e r . c o m free' dish.
(iii) Osmosis does not occur in dead tissues as observed in C.
(1b) Role of diffusion in the activities of organisms:
(i) Gaseous exchange in the gills e.g. fish
(ii) For movement of oxygen from the maternal blood into the placenta
(iii) Movement of carbon dioxide out of the foetus into the placenta
(iv) Movement of oxygen out of the leaf through the stomata during the day
(v) Absorption of end products of digestion by the villi of the ileum into the blood.