Observing Movement of Molecules Through a Cell Membrane

Name: ______Observing Movement of Molecules Through a Cell Membrane All cells have a cell membrane. In plant cells, the cell membrane is located just inside the cell wall. In animal cells, the cell membrane forms the outer covering of the cell. The cell membrane allows needed material to enter the cell and harmful waste products to exit the cell. This process by which materials enter and leave the cells is called diffusion. Diffusion is the movement of molecules from an area where there are more molecules to an area where there are fewer. Osmosis is a special kind of diffusion. It is the movement of water across the membrane. Problem: Does a cell membrane show selectivity in allowing material to pass through? Material: 2 plastic cups, 2 raw eggs in shell, vinegar, corn syrup, water, plastic wrap, rubber band, paper clip, paper towel

Procedure: 1. Place an egg in a plastic cup. Fill the cup with vinegar until it covers the egg. Measure the amount of vinegar. Record in the chart. 2. Cover the cup with plastic wrap and secure it with a rubber band. 3. Leave the egg for 48 hours. 4. Remove the plastic wrap. Measure the amount of vinegar. Pour it out. Be careful not to burst the egg. Describe the egg in Data Table 1 5. Get a new cup and put in the egg. Fill the cup with corn syrup unit it covers the egg. Measure the amount of corn syrup you use. 6. Cover the cup with plastic wrap and secure it with rubber band. 7. Let it sit for 48 hours. 8. Remove the plastic wrap. Measure the amount of corn syrup in the cup then pour it out. Describe the egg in data table 1. 9. Get a new cup and put in the egg. Fill the cup with water until it covers the egg. Measure the amount of water. 10. Cover the cup with plastic wrap and secure it with rubber bands. 11. Let is stand for 48 hours. 12. Remove the egg. Measure the amount of water. Pour out the water. Describe the egg in data table 1. You can pop the egg over a trash can or throw it out. DATA TABLE 1 Day Shape of Egg Texture of egg Amount of vinegar(beg) –

Amount of vinegar(end) –

Amount of syrup(beg) –

Amount of syrup(end) –

Amount of water(beg) –

Amount of water(end) –

Conclusion: 1. Vinegar is made of acetic acid and water. When the egg was placed in vinegar, which way did the water molecules leave?

2. How do you know? 3. What happened to the amount of vinegar after setting for 2 days. Explain what happened.

4. What happened to the amount of syrup after two days? Explain how this happened.

5. What happened to the amount of syrup after two days? Explain what happened.

6. Explain why fresh fruits are sprinkled with water at the market.

7. Road are sometimes are covered with salt to help with ice. Explain what road salt would do to the plants along side of the road.

8. If a lawn is fertilized and does not rain, the grass often dies. Explain why.