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© Boardworks Ltd 20091 of 10. © Boardworks Ltd 20092 of 10 What is osmosis? water glucose partially- permeable membrane (dialysis tubing) Osmosis is the.

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Presentation on theme: "© Boardworks Ltd 20091 of 10. © Boardworks Ltd 20092 of 10 What is osmosis? water glucose partially- permeable membrane (dialysis tubing) Osmosis is the."— Presentation transcript:

1 © Boardworks Ltd 20091 of 10

2 © Boardworks Ltd 20092 of 10 What is osmosis? water glucose partially- permeable membrane (dialysis tubing) Osmosis is the diffusion of water molecules from a low concentration solution to high concentration solution, across a partially-permeable membrane. A partially-permeable membrane has holes in it that permit water molecules through but are too small to allow larger molecules through. Osmosis can be demonstrated using dialysis tubing filled with a solution and placed in a beaker of pure water.

3 © Boardworks Ltd 20093 of 10 Dilute vs. concentrated Concentrated solutions have a low concentration of water molecules. Dilute solutions have a high concentration of water molecules. During osmosis, water molecules diffuse from pure water or dilute solution to more concentrated solutions. pure water dilute solution concentrated solution

4 © Boardworks Ltd 20094 of 10 Predicting osmosis

5 © Boardworks Ltd 20095 of 10 Osmosis in action

6 © Boardworks Ltd 20096 of 10 Osmosis and cells Plant and animal cells are surrounded by a partially- permeable plasma membrane. This allows water and other small molecules to diffuse across. plant cell red blood cell cell wall Plant cells additionally have a strong cell wall surrounding the membrane which offers support and protection. plasma membrane

7 © Boardworks Ltd 20097 of 10 Osmosis and plant cells

8 © Boardworks Ltd 20098 of 10 Osmosis and animal cells Animal cells do not have a cell wall. This means they respond differently to plant cells to the gain and loss of water. In concentrated solutions, water loss causes the cells to shrink. When this happens to red blood cells, it is called crenation. In dilute solutions, osmosis can cause animals cells, such as red blood cells, to swell up and burst. This is called lysis.

9 © Boardworks Ltd 20099 of 10 Osmosis and animal cells

10 © Boardworks Ltd 200910 of 10 Osmosis and animal cells In order to remain healthy, animal cells need to maintain an isotonic water balance. This means that the water concentration both inside and outside the cell are equal. The concentration of water and salt in the blood are controlled by the kidneys. The kidneys are controlled by the portion of the brain called the hypothalamus. hypothalamus


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