Egg Diffusion Lab Analysis

In this lab we answered the question: How and why does a cell's internal environment change, as it's external environment changes? We did this by placing one egg in a cup of sugar water and one egg in a cup of deionized water to see how these conditions would affect the egg. We measured the before and after circumference and mass of the eggs to find that the egg in sugar water shrunk and the egg in water grew.

1) As the sugar concentration increased the mass of the egg decreased by an average of 47.25% and the circumference decreased by an average of 22.94%. This change occurred because the sugar water solution was hypertonic to the egg, causing the egg to loose water and therefore shrink. The solvent of water diffuses from a lower concentration to a higher concentration to try to balance the amount of solvent and solute. However, the solute of sugar water couldn't move across the membrane into the egg because it's too large, causing the egg to only loose water and not gain sugar water.

2) The cell's internal environment changes as the external environment changes because cells naturally diffuse molecules in and out of its membrane through passive diffusion. Therefore, whatever molecules are outside the cell, this will affect what the concentration inside of the cell. When we put the egg in vinegar, it grew because vinegar is a solvent that diffused into the membrane. The external environment of the cell was the vinegar which affected the internal environment when the vinegar entered the cell, causing it to expand. However, when the egg was placed in sugar water, which is a solute, the egg shrunk because the solvent diffused out of the membrane to the external high concentration of solute outside the cell.

3) This lab demonstrates the biological principle of passive diffusion. During passive diffusion, transport proteins act as pores that allow molecules to slide through like a straw. This diffusion also acts as a filter because molecules that are too large cannot diffuse through the transport proteins. The solute of sugar water cannot passively diffuse through the cell membrane because its molecules are too large.

4) Fresh vegetables are sprinkled with water at markets to maintain turgor pressure. The vegetables look more appealing to customers when they are not shriveled up and water diffuses into the vegetables, causing them to expand. As humans, we shouldn't drink too much salt water because it causes our cells to loose water. The water in our cells diffuses to the high concentration of salt outside the cell, causing our cells to shrink and eventually die. Similarly, the plants along the side of the road shrivel up when salted because the water inside the plant cells diffuses out.

5) I would create an experiment testing whether plant and animal cells react the same when placed in sugar water. Would they both loose the same amount of water? Would they loose water at the same rate? I would test for the difference of diffusion in plant and animal cells.