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Coordinated Science II Osmosis and Diffusion Practice Problems Name:_________________________________________ Date:______________ Class:______ 1. Define the following terns a. Osmosis- when water moves across a semi-permeable memebrane from a high water potential to a low water potential b. Diffusion- the movement of molecules down a concentration gradient form high concentration to low concentration c. Concentration gradient- the difference in the concentration of a substance from one location to another d. Hypertonic- water leaves the cell to enter the more concentrated solution e. Isotonic- Water enters and leaves at the same rate f. Hypotonic- water enters the cells since the cytoplasm is more concentrated 2. For each example below, explain if it describes (i) diffusion, (ii) osmosis, or (iii) neither. Explain your answer in each case. a. Water moves from a dilute solution in the soil into the cells in a plant’s roots. ii- water is moving from a high water potential to a low water potential b. Saliva flows out of the salivary glands into your mouth. iii- neither c. A spot of blue ink dropped into a glass of still water quickly colors all the water blue. i- diffusion since the ink molecules are moving from a high concentration to a low concentration. Coordinated Science II Osmosis and Diffusion Practice Problems d. Carbon dioxide goes into a plant’s leaves when it is photosynthesizing. ii-diffusion, carbon dioxide is moving from a high concentration to a low concention 3. Explain each of the following. a. Diffusion happens faster when the temperature rises. The molecules of solution that are heating up are moving faster and therefore spreading the solution faster b. Oxygen diffuses out of a plant leaf during daylight hours. Oxygen is moving from the high concentration inside the leaf to low concentration in the air c. Water molecules can pass through dialysis tubing, but starch molecules cannot. Water molecules can pass through tubing due to its small size, starch molecules are too large to pass through the semi-permeable tubing. d. An animal cell bursts if placed in pure water. The animal cell takes in the water, but since the animal cell does not have a cell wall to push back on the growing pressure of the cell membrane, the cell membrane will burst. e. If a plant is short of water, its leaves lose their firmness and the plant wilts. Is there is not enough water in the cell, then the cell membrane won’t be pushing against the cell wall and therefore the cells are not firm. 4. The drawing shows the outline of a human cell. Copy the drawing and make two further drawings to show how the cell would appear if it were to be immersed for a few minutes in a solution with: a. a lower water potential than its own cytoplasm Coordinated Science II Osmosis and Diffusion Practice Problems Drawing should show shriveled cell given that the water has been removed from the cell into the solution b. a higher water potential than its own cytoplasm. Drawing should show an inflated cell, or a cell exploding since the water is going from the outside to the inside. 5. The graph shows the concentration of a substance inside and outside a cell. If the substance is free to move by diffusion, which way will it move? From the cytoplasm to the outside cell a. If, after some hours, the concentration has not changed, what assumption would you make about the movement of the substance across the cell membrane? There are too large to cross through the memebrane 6. Cereal plants were growing in a field. The field was then flooded with sea water. Suggest why the sea water causes plants to die. The sea water would create a hypertonic environment where water is rushing from the cells into the salt water solution. The water loss results in cells being plasmolyzed and not being able to function correctly 7. Each of these statements was made by a candidate in an examination. Each one contains at least one error. Decide what is wrong with each statement and rewrite it correctly. a. If dialysis tubing containing a sugar solution is put into a beaker of water, the sugar solution moves out of the tubing by osmosis. If a dialysis tubing containing a sugar solution is put into a beaker of water, the water moves into the tubing by osmosis. Coordinated Science II Osmosis and Diffusion Practice Problems b. Plant cells do not burst in pure water because the cell wall stops water getting into the cell. Plants cells do not burst in pure water because the cell wall pushes back against the cell membrane. c. Animal cells break away from the cell wall in a concentrated sugar solution. Animal cells membrane shrivel up in a concentrated sugar solution. d. When a plant cell is placed in a concentrated sugar solution, water moves out of the cell by osmosis through the partially permeable cell wall. When a plant cell is placed in a concentrates sugar solution, water moves out of the cell by osmosis through the partially permeable cell membrane. 8. The diagram at the right represents (not to scale) molecules of a salt dissolved in the bottom layer of water in a beaker. Make two similar diagrams to show the distribution of salt molecules (a) after a few minutes, (b) after several hours. a. the salt molecules will be diffusing upwards b. the salt molecules are throughout the beaker 9. When meat is salted, bacteria cannot grow on it. Suggest a reason for this. The meat has low water potential, and bacteria would have high water potential therefore the water will move from the high water potential of the bacteria to the low water potential of the meat. 10. The diagram at the right shows a vessel that contains a concentrated and a dilute solution separated by a partially permeable membrane. Draw a similar diagram to show the liquid levels after an hour or two. The dilute solution should be lower because it is going from a dilute solution to a concentrated one Coordinated Science II Osmosis and Diffusion Practice Problems