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Osmosis. IB Biology Topic 2. Key Vocabulary for Osmosis. Water Potential: The tendency of water molecules to move from one place to another Hypotonic Solution: Means that the solution is more dilute than the cell-sap
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Osmosis IB Biology Topic 2
Key Vocabulary for Osmosis • Water Potential: The tendency of water molecules to move from one place to another • Hypotonic Solution: Means that the solution is more dilute than the cell-sap • Isotonic Solution: Means that the solution has the same water potential as the cell-sap • Hypertonic Solution: Means that the solution has a lower water potential than the cell-sap • Endosmosis: The transfer of water into the cytoplasm through a semi-permeable membrane • Turgidity: The pressure inside the cell pushing against the cell-wall when it increases water potential • Plasmolysis: When the cell loses water and the cell-membrane is pulled inwards, it is plasmolysed • Turgor Pressure: The pressure inside the cell when it becomes turgid • Concentration Gradient: The difference of concentrations between two regions (difference of concentration between high & low region)
Osmosis Osmosis is the net movement of water molecules across a partially permeable membrane from an area of lower osmotic potential to an area of morenegative osmotic potential.
Water potential • Water potential is a measure of water molecule potential for movement in a solution. • Water always moves by osmosis from less negative to more negative water potential. • The highest possible water potential is that of pure water which is 0, all other solutions have a negative water potential. • Water potential is measured in Pa.
Hypertonic Solutions • Hypertonic solutions contain a high concentration of solute relative to another solution for example the cells cytoplasm. • Water diffuses out of a cell when it is placed in isotonic solution which causes the cell to shrivel.
Hypotonic Solutions • Hypotonic Solutions have a high concentration of solute relative to a different solution i.e. the cells cytoplasm. • Water diffuses into the cell when it is placed in a hypotonic solution, this means the cell swells and possibly explodes.
Isotonic solutions • Isotonic solution has the same concentration as another solution for example the cells cytoplasm. • Water diffuses in and out of the cell at the same rate when placed in an isotonic solution. • The fluid surrounding body cells is isotonic.
Now try your osmosis worksheet • Diffusion and osmosis practice problems