BIO 2 GO! Osmosis 3121

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1 BIO 2 GO! Osmosis 3121 Osmosis is a process. Osmosis is the movement of water from an area of high water concentration through a membrane to an area of lower water concentration. Osmosis continues until the water concentration on both sides of the membrane is equal.

2 Osmosis 3121 Water is very important to all living cells. Because of this, water must flow into and out of cells. Water is crucial to all living organisms. It must be present inside and outside of all cells in order for molecules of nutrients and oxygen to move into the cell and for wastes to move out of a cell. All of the chemical reactions in a cell can only take place if water is present. Substances can dissolve in water, so water is a solvent. Since water dissolves so many substances, it is known as the universal solvent. The substance that gets dissolved in water is called a solute, like salt. When a solute is dissolved in a solvent, the mixture is called a solution, in this case salt water. Concentration refers to the amount of solute or solvent in a solution. The process that describes the movement of water from an area of high water concentration into an area of lower water concentration is called osmosis (or from low solute concentration to high solute concentration). Water molecules are constantly moving. The movement of water molecules into or out of a cell depends on the concentration of the water molecules inside and outside the cell. Water always moves from a higher water concentration into a lower water concentration, or from area of low solute to high solute concentration. You will need to be able to predict which way water will flow according to osmosis.

3 Look at the picture above: If cells that are usually 75% water are put into distilled water (100% water), they will swell and burst. If the same type of cells are put into salty water (60% water), they will shrink. REMEMBER THIS!!! Water molecules always move from an area of high concentration to an area of lower concentration (0r from low solute to high solute concentration. (osmosis) Draw the following If there is a greater concentration of water molecules outside of a cell than inside of a cell, then the water molecules will move into the cell faster than they will move out. So the cell will begin to fill up with water until the concentration is the same inside and outside of the cell. In the space below, draw a circle to represent a cell. On the outside of the cell, draw a large number of X s to indicate water molecules. On the inside of the cell, draw a smaller number of X s. Since the concentration of water is greater outside of the cell, the water will pass through the membrane into the cell. So the cell will grow larger as it takes in more water. Draw an arrow which shows water moving into the cell.

4 Question 1. According to osmosis, which direction will water always flow in a cell? Question 2. What would happen to a cell if the flow of water to the inside of a cell continued without stopping? Question 3. Explain how your drawing explains the process of osmosis. Draw the following If there is a higher concentration of water molecules inside of a cell than outside, then the water molecules will move out of the cell faster than they will move in. In the space below, draw a large circle to represent a cell. On the inside of the cell, draw a large number of X s to represent a large concentration of water molecules. On the outside of the cell, draw a smaller number of X s to represent a lower concentration of water. Since the concentration of water is greater inside of the cell than outside, the water will move out of the cell until both the inside and outside are equal. So the cell will shrink because it is losing water. Draw an arrow which shows the net movement of water out of the cell.

5 Question 4. Look at the drawing above. What would happen to the cell if osmosis continued without stopping? Question 5. Explain how your drawing explains the process of osmosis. Question 4. According to the process of osmosis, what would happen to the flow of water if the concentration of water inside and outside of a cell were the same? REMEMBER THIS!!! The process of osmosis will continue until the inside and outside of a cell have the same concentration of water. Draw the following If the concentration of water molecules is the same inside and outside the cell, then the same number of water molecules will move into and out of the cell. So the cell will not change its shape because it is not gaining or losing any water. In the space below, draw a large circle to represent a cell. On the inside of the cell, place 3 X s to represent the water concentration. On the outside of the cell, draw 3 X s to represent the water concentration outside of the cell. Note that the water concentration is the same on both sides of the cell membrane. Since the water concentration is the same inside and outside of the cell, water moves in and out at the same rate. Because of this, the cell will not change its shape. Since there is no net movement of water, do not draw any arrows.

6 Question 5. From your drawing above, what would happen to the cell if the process of osmosis continued without stopping? Question 6. Explain how your drawing above explains the process of osmosis. REMEMBER THIS!!! If the concentration of water inside and outside of a cell are the same, then there is no net movement of water. Summary The movement of water molecules from a high water concentration across a membrane into a lower water concentration is called osmosis. It will occur until the water molecules are spread out evenly on the inside and outside of a cell. A cell could die by either bursting or shrinking if it is placed in an environment that has a water concentration that is different from the water concentration on the inside of the cell. Interesting Scientific Fact: If you take a living organism from the Chesapeake Bay and place it in pure water, it would absorb water, swell, and probably die. Likewise, if you put salt on a slug, the salt draws the water out of the slug because it lowers the water concentration outside of the cell. If allowed to continue, the slug will shrink and die.

7 Osmosis Test Yourself 1. Draw a picture which shows the process of osmosis in which the concentration of water is greater inside of the cell than outside. Indicate which direction the water will move. 2. Draw a picture which shows the process of osmosis in which the concentrations of water inside and outside of the cell are the same. Indicate which direction the water will move. 3. Draw a picture which show the process of osmosis in which the concentration of water is greater outside of the cell than inside. Indicate which direction the water will move.

8 True or False 1. The uneven movement of water molecules is called osmosis. 2. Osmosis occurs when there are equal concentrations of water inside and outside a cell. 3. If a cell is surrounded by a greater concentration of water than what is has on the inside, more water molecules will move out of the cell than in. 4. If a cell is surrounded by a greater concentration of water than what it has on the inside, more water molecules will move into the cell than will move out. 5. If a cell is surrounded by a greater concentration of water than what it has on the inside, the cell may burst. 6. If a cell is surrounded by a greater concentration of water than what it has on the inside, the cell may shrivel. 7. If a cell is surrounded by a lower concentration of water than what it has on the inside, more molecules will move out of the cell than will move in. 8. If a cell is surrounded by a lower concentration of water than what it has on the inside, more molecules will move into the cell than will move out. 9. If a cell is surrounded by a lower concentration of water than what it has on the inside, the cell may burst. 10. If a cell is surrounded by a lower concentration of water than what it has on the inside, the cell may shrivel. 11. If a cell has a 99% water solution inside, and is put in a 95% water solution, the cell may burst. 12. If a cell has a 95% salt solution inside, and is put in a 99% salt solution, the cell may burst. 13. Osmosis is the movement of water from an area of water high concentration into an area of lower water concentration. 14. Osmosis is the movement of water from a low water concentration to a higher water concentration. 15. Osmosis may cause some living things to die. 16. Osmosis refers to the movement of food through a cell membrane.

9 Fill in the Blank into out of swell shrivel osmosis same greater concentration lower concentration evenly 1. The uneven movement of water molecules is called. 2. If there is a of water molecules outside a cell than inside, water molecules will move into the cell faster than they will move out. 3. If there is a of water molecules outside a cell than inside, water molecules will move out of the cell faster than they will move in. 4. If the concentration of water molecules is the inside and outside the cell, then the same number of water molecules will move into and out of the cell. 5. If a cell is placed in a solution that has a water concentration higher than it, the cell may. 6. If a cell is placed in a solution that has a water concentration lower than it, the cell may. 7. Osmosis occurs until the molecules of water are spread out inside and outside of the cell. 8. If a cell that has 97% water inside is placed in a solution that is 100% water, the water molecules will move the cell faster than they will move of the cell. 9. The movement of water from an area of high concentration into an area of lower concentration is called.

10 Answer the following. 1. What is osmosis? 2. Why must living cells have water inside and outside? 3. When will water molecules move into a cell by osmosis? 4. When will water molecules move out of a cell by osmosis? 5. When does osmosis stop? 6. Why is osmosis important to a cell? 7. Draw a picture and predict what would happen in the following example: A freshwater organism was placed in the Chesapeake Bay where the concentration of water outside of the organism would be less than the inside.