Osmosis Across Egg Cell Membranes 

Author(s): Krista Botton and Marissa Mullen  Longitudinal Study
SED 695B; Fall 2007 
Research Question: How do different solutions effect the movement of water across an egg cell membrane?


Standards addressed: Biology Standard 1a: Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.

Independent variable 
Dependent variables 
Controls 
Series 
Various solutions: 
Mass change of eggs  Temperature 
Mass change of each egg 
Materials 
Procedures 

Eggs Any other solution of your choice 
Place eggs in a beaker (or in cups) with enough vinegar to cover to dissolve shells from eggs. Place a styrofoam cup with a small amount of water on the top to hold the eggs under the vinegar. (This usually takes approximately 48 hours  if set up on Friday eggs are ready to go on Monday). Part A 1. Carefully remove the eggs from the vinegar and dry the eggs. Mass the eggs and record their weight in the data table. 2. Place the eggs in separate beakers (or cups) and add 100 mL of the test solutions to the eggs and let them sit for 24 hours. (You may use any solutions that you like, we used Karo's light syrup, DI water, a can of soda, and a 20% salt solution by volume). 3. The next day remove the eggs from the cups, dry and mass the eggs. Record their mass in the data table. Part B Since the syrup eggs have the most dramatic loss of mass because of water through osmosis, they are the best eggs to use for the second part of this lab, but you may choose to have different groups use eggs from varying solutions. Place the plasmolyzed eggs from the syrup into DI water. Remove the egg at 10 minute intervals, dry and mass the egg, recording the mass in the data table each time. 

Part A Data Table
Part B Data Table

Data tables can be adjusted to fit the needs of your class. Columns can also be added to Part A data table for mass change and/or percent of mass change in each egg. Columns may also be added for students to record observations about the changes in the egg and/or solutions. 

Part A Data Table with Sample Data
Part B Data Table with Sample Data

Our sample data. Unfortunately, we started with 3 eggs for each solution but two of the eggs broke :(  
Graphs of Part A Egg Mass Changes Graph of Part B Egg Mass Changes

These graphs show the changes in mass for each egg in our sample data.  

Here are some pictures of this lab in progress. 

References & Links: http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm http://sps.k12.ar.us/massengale/egg_osmosis_sample1_lab.htm
