This means that when the plant cells are placed in a strong sugar solution (where there is more sugar than water.) there will be a decrease in weight and volume. This process is defined as plasmolysis. This is where the cell membrane pulls away from the cell wall, this is because a lot of water has been moved from the cell as the plant cell has the strong concentration of water and the solution has a weak concentration the water will move from the plant top the water. Sometimes the cell will shrivel up completely and it becomes flaccid.
Cells placed in distilled water take up water by osmosis. This happens because the cell contains dissolved chemicals and therefore has a lower water potential than the distilled water surrounding it. As there are more water molecules outside the cell, more go in to the cell than out of it. The net movement of the water molecules is into the cell, and the cell will increase in mass. Eventually the cell stops taking up water, even though the concentrations inside and outside are not even.
The cell membrane is similar to the membrane mentioned above, so the cell would lose water because of osmosis if it were placed in an environment in which water concentration is greater than that of the cell. A solution is isotonic if the concentration of dissolved substances is the same as the concentration inside the cell. Osmosis does not occur in an isotonic solution. A hypotonic solution is a solution in which the concentration of dissolved substances is lower than the concentration inside the cell. If a cell were put in a hypotonic solution, osmosis will cause water to move through the cell membrane into the cell.
The cell will stay the same size. If the solution has a lower concentration of water than the cell the cell will lose water by osmosis. Again, water crosses the cell membrane in both directions, but this time more water leaves the cell than enters it. Therefore the cell will shrink and become 'flaccid' Potato plant cells:- Plant cells always have a strong cell wall covering them.
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 concentration of water), water will move across the semi-permeable membrane into the cell (lower concentration of water) by osmosis, making the cell swell. This cell is now turgid. If this were done with potato cells the cells would increase in mass because of the extra water.
The chain of events starts with water leaving the cell through the cell membrane by osmosis because the water concentration outside is lower than that in the cell. As water is lost the vacuole gets smaller as it is used to top the cytoplasm up. This reduces the volume of the cell contents so the membrane begins to shrink away from the cell wall. At first it will stay in contact with the wall at several points, but pretty soon it will shrink away from the wall completely. If the process continues the vacuole will disappear completely and the cytoplasm will continue to shrink.
Osmosis Investigation What is Osmosis? Osmosis is basically the movement of water molecules from a dilute system solution to a concentrated solution, through a partially permeable membrane. Water molecules are able to pass through the cell membrane because they diffuse whereas sugar molecules are larger and cannot diffuse as easily therefore not being able to pass through. Cell membranes are like visking tubes because they will let some substances through but not others. They are partially permeable membranes.
-From Encarta 2001 In osmosis, a solvent (often water) moves from a region of low concentration to a region of high concentration through a semi-permeable membrane. Here, water molecules diffuse into the concentrated sugar solution because the water molecules are small enough to move through the membrane. The larger sugar molecules are unable to move through the membrane into the water solution. Osmosis will stop when the two solutions reach equal concentrations on either side of the membrane[IMAGE] . In the investigation I will be doing, it is osmosis in plant cells
Osmosis is simply the movement of water molecules from a region of high water concentration to a region of low water concentration, across a semi-permeable membrane. A semi-permeable membrane is a barrier with small holes in, the holes are so small that only water can pass through them, bigger molecules like glucose cannot. The water molecules actually pass both ways through the membrane but because there are more on one side than the other there is a steady flow into the region with the fewer water molecules, i.e. into the stronger solution (of glucose). This causes the glucose-rich region to fill up with water.
Water particles are small and can therefore easily fit through the material; however, larger particles such as salt or glucose are too big to fit through the material. Osmosis has a significant effect on living cells. Animals cells will burst in pure water because, as the cytoplasm is fairly concentrated, the water, which is less concentrated, will enter the cell. As the dissolved substances in the cytoplasm are larger, they cannot escape so the cell becomes swollen and may burst. If an animal cell is placed into a more concentrated solution, the water in the cell will flow... ... middle of paper ... ...rmine the molar concentrations.