Name ________________________________ Hour _________________ Egg Osmosis Lab Purpose: The purpose of this lab is to demonstrate what happens when an animal cell is exposed to varying osmotic environments Questions to Think About: What happens when a cell is subjected to a solution where the water concentration is higher than that inside a cell (hypotonic solution)? What happens when a cell is subjected to a solution where the water concentration is lower than that inside a cell (hypertonic solution)? What happens when a cell is subjected to a solution where the water concentration is equal to that inside a cell (isotonic solution)? The cell is like a salty sea that is mostly water. The cell membrane in an animal cell is both a protective barrier and a filter to keep unwanted materials out and bring needed materials inside. Water can move freely through the cell membrane with osmosis. So can small molecules such as sodium and calcium ions. Large molecules like polysaccharides and proteins need assistance in moving through the cell membrane. In this experiment, you will be looking at the movement of water. Materials: 3 Eggs 3 Plastic cups Water Vinegar Corn syrup Paper towels Procedure: Day 1 1. Grab a cup and mark it with your period number, group number, and water, using a sharpie. 2. One group member should take an egg from the egg crate, weigh it on a scale and place the egg in the correctly marked cup. 3. Record the starting weight of the egg in the table on the student worksheet. 4. Gently pour water into the cup so that the egg is just covered by it. 5. Repeat steps 1 thru 4 with an egg for vinegar, and an egg for corn syrup instead of water. 6. Put your cups together on a tray designated by your teacher. 7. Once you have completed this part of the lab, answer the pre-lab prediction questions on the student worksheet. Name ________________________________ Hour _________________ Day 2 1. One group member should take the egg gently out of each cup, rinse gently under tap water, pat it dry with a paper towel, and weigh it on a scale. 2. Record the final weight of each egg in the table of your student worksheet. 3. Dispose of the liquids down the drains, and throw the eggs into the trash. 4. Once you have done this, complete the rest of the table, and answer the analysis questions. Name ________________________________ Hour _________________ Student worksheet Pre-Lab Predictions: 1. What will happen to the weight of the egg in corn syrup? Why? 2. What will happen to the weight of the egg in the water? Why? 3. What will happen to the weight of the egg in the vinegar? Why? Weight at the start (grams) Soaking Solution Weight at the end (grams) Difference in Weight (end-start) Water Vinegar Corn Syrup Analysis Questions: 1. How did the results compare to your pre-lab predictions? 2. Which of the solutions were hypertonic? What is your evidence? 3. Which of the solutions were hypotonic? What is your evidence? Increase or Decrease?