Answers
38. (b) be smaller in size, (The cell 0.5% salt placed in a hypertonic solution of 1.5% salt)
39. (a) cell A will swell more than cell B
Explanation
The process where water moves across a membrane is called osmosis. Salt solution triggers osmosis by attracting the water and making it to move towards it, across the membrane. If the concentration of the salt inside a cell is the same as that concentration outside the cell, the water level will stay the same and there will be no change in shapes of the cells because they are placed in an isotonic solution. A cell cannot loose or gain water when placed in an isotonic solution.
The movement of water in a cell occurs towards the highest solute concentration. If a cell is in a hypertonic solution (> 5% glucose) solution, the water will move from the lower concentration of solute to the region with the highest solute concentration to maintain equilibrium of osmotic pressure. Cell B that is placed in a 5% glucose will lose more water and its size will be smaller than that of cell A because it would have wilted more than cell A which was placed in a 2% glucose solution.