My aim to find out when the sugar solution’s concentration is high or low it will expand or reduce. Plant cells always have a strong cell wall surrounding them. When the take up water by osmosis they start to swell, but the cell wall stops them from bursting. When they are put in dilute solutions, plant cells turn out to be “turgid” (swollen and hard). When the pressure inside the cell increases; No more water can’t enter the cell because the internal pressure of the cell is really high. “When plant cells are placed in concentrated sugar solutions they lose water by osmosis and they become “flaccid”; this is the exact opposite of “turgid”. If you put plant cells into concentrated sugar solutions and look at them under a microscope you would see that the contents of the cells have shrunk and pulled away from the cell wall: they are said to be plasmolysed.” When plant cells are placed in a solution which has exactly the same osmotic strength as the cells they are in a state between turgidity and flaccidity. We call this incipient (about to be) plasmolysis. Although their cells are not plasmolysed, they are not turgid and so they do not hold the leaves up into the sunlight. (7) If red blood cells are placed in a solution with a lower solute concentration than is found in the cells, water moves into the cells by osmosis, causing the cells to swell; such a solution is hypotonic to the cells. When red blood cells are placed in pure water, water rapidly enters the cells by osmosis and causes the cells to burst, a phenomenon known as haemolysis. If the red blood cells are placed in a solution with a higher solute concentration, water moves out of the cell by osmosis. (8) **When the osmotic pressure of the solution outside the blood cells in higher than the osmotic pressure inside the red blood cells, the solution is hypertonic. When the solution outside of the red blood cells has a lower osmotic pressure than the cytoplasm of the red blood cells, the solution is hypotonic. The cells take in water in an attempt to equalize the osmotic pressure, causing them to swell and potentially burst. In this picture below a red blood cell is placed in a beaker of purified water (all water with no salt or sugar in it). As there is a higher concentration of water outside the cell, water enters the cell by osmosis. In this case too much water enters and the cell swells to the point of bursting open. In the end pieces of cell membrane are left in the water. (9) A semi permeable membrane is a barrier that permits the passage of some substances but not others. Cell membranes are described as selectively permeable because not only do they allow the passage of water but also allow the passage of certain solutes (dissolved substances). Osmosis occurs across a semi permeable membrane, which has tiny holes in it. These holes are small enough for water molecules to pass through but larger molecules cannot pass through. Most plant cells are turgid at all times. This supports the weight of the plant, which is especially important where there is no woody tissue, such as leaves, shoot and root tip. If the plant loses water faster than it can be absorbed the cells lose turgid pressure and become flaccid. This causes the plant to wilt. Most plants will wilt if seawater floods them. Seawater contains many chemicals in solution, such as salt. Osmosis will move water across the plant cell membrane, from the weaker to the stronger solution. Osmosis is the movement of water from a high water concentration to a low water concentration through a partially permeable membrane (it is placed in the cell membrane and has tiny gaps in it and just lets tiny water molecules move through it) It doesn’t let large solute molecules through. Osmosis takes place in all living cells. Plants absorb water from the soil by osmosis through their root hair cells. Plants use water for several vital processes including photosynthesis and transporting minerals. (10 -S.E...
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