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Diffusion and Osmosis - Coggle Diagram
Diffusion and Osmosis
Diffusion is the movement of molecules of a liquid or gas from a region of high concentration to a region of low concentration across a concentration gradient (it is a passive process i.e. does not require energy)
Examples of Diffusion
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If a cell uses oxygen in respiration it will have a low concentration of oxygen. Concentration outside the cell is higher than the concentration inside the cell so oxygen will diffuse into the cell
If a leaf is carrying out photosynthesis then it will be producing oxygen. The concentration of oxygen in the leaf will be high. If the concentration of oxygen in the leaf is higher than concentration of oxygen outside in the air then oxygen will diffuse out of the leaf
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Osmosis is the movement of water molecules from high concentration of water to a low concentration of water across a semi-permeable membrane
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To Demonstrate Osmosis
- Soak length of visking tubing in water (visking tubing is a semi-permeable membrane and soaking it makes it soft and pliable)
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9.Remove the tubes from the water, dry them and weigh them. Note how full each tube is
Results: Tubing with starch solution expands and becomes more full. It gains weight - this happens because water moves due to osmosis from a high water concentration to a low water concentration in the visking tubing
Osmosis and Plant Cells
Plant cells are surrounded by cell walls which are fully permeable. However the cell membrane inside the cell wall is semi-permeable
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Plasmoysis When plant cells are placed in salty water (a concentrated solutions), they lose turgor and become weaker. The cells are said to be plasmolysed. If plant cells lose turgor, plant is seen to wilt. This is temporary and can be reversed by placing plant cells in less concentrated solutions than their cell contents e.d. water them
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