Mrs. Sangster Biology
LABORATORY INVESTIGATION: Osmotic Transport in Cells
Name______
Class Color______
PART A: OSMOSIS
In this investigation you will use a fresh egg to determine what happens during the process of osmosis. You will be measuring the amount of water that passes through the membrane lining the shell of the egg, while the egg is in a vinegar solution, corn syrup and dyed water or (your choice).
MATERIALS: fresh egg in shell,1 cup, white vinegar, corn syrup (Karo, for example), water source, food coloring, your choice of liquid (must discuss prior with teacher), scale (digital or triple beam balance), piece of string to measure circumference and metric ruler.
DAY 1 PROCEDURE:
1. Label your cup with your name and class color.
2. Weigh the egg in gramsusing the scale. Always place the egg in your cup to move around the room. (Record on data sheet)
3. Measure the circumference of the egg in centimeters with your string and ruler …before you add it to the vinegar solution.(Record on data sheet)
4. Using the graduated cylinder, measure out 200 mL of vinegar. Pour the vinegar in the cup covering the egg.
5. Observe the egg for about 3-5 mins and record qualitative observations.
6. Put the cup in the designated area for your class and allow it to stand for 24-48 hours.
DAY 2 PROCEDURE:
7. Observe what has happened to your egg. Record on the data sheet.
8. Carefully remove the egg from the vinegar. It is quite fragile now as the shell is dissolved. Very gently rinse the egg in waterfor only a few seconds–it will be very fragile and rinse the cup. Always place the egg in your cup to move around the room. Measure the circumference of the egg with your string and then mass your egg on the scale. (Record on data sheet)
9. Add enough corn syrup to completely cover the egg (about 200 ml).
10. Place your egg in the designated area for your class.
DAY 3 PROCEDURE:
11. Carefully remove the egg from the syrup cup, rinse it only for a few seconds and then rinse out the cup with a paper towel and water. Record your qualitative observations of the egg's appearance on the data sheet.
12. Measure the circumference of your egg using the string and ruler. Mass your egg on the scale and then record the mass and circumference on the data sheet.
13. Your Choice:If you brought a different liquid that has been approved you may use it in this step. Place 200ml of the liquid in the cup covering the egg.
14. Dyed Water Choice: Place 200 mL of water in your cup covering the egg. Add 3 drops of food coloring of your choice into the water. Place the egg in the designated area for your class.
Day 4 PROCEDURE:
15. Remove the egg from the water and record your qualitative observations of its appearance. Measure the circumference and mass the egg. Discard the egg in the trash can.
17. Answer the questions on the data sheet.
PART B: Lab Questions
1. When the egg was placed in the vinegar, in which direction did the water molecules move?
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2. Explain why this happened? (Refer to question 1)
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3. How can you explain the amount of liquid remaining when the egg was removed from the syrup? What happened?
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4.When the egg was placed in the water solution after being removed from the syrup, what direction did the water move? Why?
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5. Which liquids were hypotonic? Explain your reasoning.
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6. Which liquids were hypertonic? Explain your reasoning?
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PART C: Real-life Applications
Use concepts from the experiment and answer the following questions of application. Explain using terms: hypertonic, hypotonic, isotonic, osmosis, high concentration, low concentration, inside the cell, and outside the cell.
1. Why do grocery store owners spray fresh fruit and vegetables with water?
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2. Roads are sometimes salted to melt ice. What does this do to plants around the roadside and why?
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3. If a bowl of fresh strawberries is sprinkled with sugar, a few minutes later the berries will be covered with juice. Why?
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4. Explain how if a shipwrecked crew drank salt water to try and survive, they would probably die. Use concepts from this lab.
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