Firuze Naim 10P
Biology Coursework 2002
Factors That Effect Osmosis In Potato Tissue
Aim
My aim is to investigate the effect of different concentrations of sucrose solution on potato chips.
Hypothesis
Osmosis is the passage of water molecules from a weaker solution into a stronger solution, through a partially permeable membrane. In this case, the tiny holes in the membrane of the potatoes will allow the water molecules to pass through in and out of the solution and the potato, depending on the concentration gradient of the two substances. So in this case, when the water concentration is lower in the tissue, the water will go inside the tissue of the potato, and the potato will gain mass. If there is very little difference in the two water concentrations, there shouldn’t be such a big change in mass. Also, if there is a higher concentration of water in the potato, then the water will go out of the potato and into the liquid solution, as osmosis is the movement of water molecules from a region of high concentration to a region of low concentration, through a partially permeable membrane. If the concentration of solution used is high then I a loss in mass will be seen, whereas if the concentration of the solution is low a gain in mass will be seen.
Scientific Explanation
Osmosis is defined as the movement of water molecules from an area of high water concentration to an area of low water concentration, across a semi-permeable membrane. In a high concentration of water the amount of sucrose is low. This could be called a weak or dilute solution. In a low concentration of water the amount of sucrose is high. This could be called a strong or concentrated solution. When a semi-permeable membrane divides two such solutions the water will move from the area of high concentration to the area of low concentration, until both sides have reached equilibrium. This can be seen in living cells. The cell membrane in cells is semi-permeable and the vacuole contains a sugar/salt solution. So when a cell is placed in distilled water (high water concentration) water will move across the semi-permeable membrane into the cell (lower water concentration) by osmosis, making the cell swell up. This cell is now referred to as turgid. If done with potato cells the cells would increase in length, volume and mass because of the extra water. If these potato cells were placed in a solution with a low water concentration, then the opposite would happen. Water would move out of the cell into the solution. In extreme cases the cell membrane breaks away from the cell wall and the cell is referred to as plasmolysed. The potato cells will have decreased in length, volume and mass.
