Osmosis
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Osmosis can be defined as the spontaneous movement of water molecules from an area of high concentration, to an area of lower concentration through a partially permeable membrane.
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Osmosis refers to the movement of water molecules only.
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The concentrated solution has low concentration of water molecules.
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A dilute solution has high concentration of water molecules.
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Osmosis can happen in either direction, that means water can move in either direction depending on the relative concentration of dissolved substance.
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Water will diffuse from a high water potential to a low water potential.
Osmosis in living cell
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The cell membrane of animal is partially permeable.
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Animal cells, which do not have cell walls, can respond adversely to change in the surrounding water pressure.
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In pure water, the plant cells take up water by osmosis and become turgid.
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In a more concentrated solution, the cell contents lose water by osmosis, and become flaccid.
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Cells have dilute solutions of sugars, amino acids and mineral ions.
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Animal cells also take in and lose water by osmosis. Animal cells do not have a cell wall, therefore they change size and shape when put into solutions of different concentration.
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In animals, the concentration of body fluids must be kept within optimal limits. Cells will not function efficiently if they lose or gain too much water by osmosis.