When the sugar concentration of the solution the egg was placed in increased, the mass and circumference of the egg both became smaller. This change was caused by the passive diffusion of water. In the solution of sugar water, sugar is the solute, and water is the solvent. The sugar water had a higher concentration of solute to solvent than the egg. Solutes like sugar are too big to diffuse across the egg's membrane, but solvents can passively diffuse across the egg membrane. Since diffusion's goal is to reach equilibrium, or the point when the concentrations of solute to solvent are equal, solvent molecules moved out of the egg's membrane in order to dilute the sugar water outside of the egg. Because water left the egg in sugar water, the egg shrank.
24 hour time lapse of our Egg Diffusion Lab. Egg on left in corn syrup, egg on right in DH2O pic.twitter.com/wdfujQyBXM— Mr. Orre's Class (@OrreBiology) October 5, 2016
A cell's internal environment changes as it's external environment changes because of diffusion. Because cells want to reach equilibrium with their surrounding solutions, they either shrink or grow, depending on their environment. When the egg was placed in vinegar, it lost its shell because vinegar is acidic. When the egg was placed in water, it grew, because the egg has more solutes than water, since pure water has no solutes. And when the egg was placed in sugar water, it shrank because the sugar water had more solutes than the egg.
This lab demonstrates the biological principal of osmosis. Osmosis is the diffusion of water across a selectively permeable membrane. This membrane refers to the egg's membrane. Because osmosis is a type of diffusion, the water will attempt to go from a low concentration of solute to a high concentration of solute in order to reach equilibrium. This is the process that happens when the egg is placed in sugar water. This lab also demonstrates the biological principal of tonicity, which is the ability of a surrounding solution to cause a cell to gain or lose water. The sugar water was a hypertonic solution, meaning the solute concentration in the sugar water was more than that inside of the egg. The deionized water was a hypotonic solution, meaning the solute concentration in the egg was more than that in the surrounding solution.
Fresh vegetables are sprinkled with water at markets because the vegetables have less water, or solvent, and more solute. Because the cells of the vegetables have more solute than their surrounding, hypotonic solution of water, the vegetables will gain water, keeping them fresh for longer. When roads are salted to melt ice, plants along the roadside may wilt. When the ice melts, the resulting water combines with the salt to form a salt water solution. Since the cells of plants have less salt than the salt water, which is hypertonic compared to the plant cells, the plants lose water, causing them to wilt.
Based on this experiment, I would like to test the tonicity of other solutions. I would like to do this so I can find solutions that are isotonic to an egg cell. I would also like to test this with different cells, but since the changes in mass and circumference would be much harder to measure, I would probably test this with different types of eggs.
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