The Eggs Lab
Olivia Jacobs
Ellie Hogg
- Introduction
One of the most important parts of cell is the semi permeable cell membrane. The cell membrane, commonly known as the plasma membrane, allows small polar molecules to pass through it while larger molecules cannot. This process is called active transport. Molecules will move through the cell membrane according to the concentration gradient (the difference in concentration of a substance from one location to another) from a hypertonic environment (an environment where there is a higher concentration of dissolved particles than a cell) to a hypotonic environment (an environment where there is a lower concentration of dissolved particles than a cell) which means that the molecules require no energy from the cell to pass through the plasma membrane. How does the concentration gradient determine the direction the molecules will move through the cell membrane? How do a hypotonic and a hypertonic environment differ?
2. Hypothesis
If one egg that has been soaked in vinegar is placed in a cup, half full of distilled water and one egg that has also been soaked in vinegar is placed in a cup of corn syrup, then the egg in distilled water will swell and the egg in corn syrup will become softer and more paper like, thinner outside layer.
3. Materials
Used in this lab were 2 foam cups, approximately three fourths cups of distilled water, approximately three fourths cups of corn syrup, a scale, a tape measure, four paper towels, and two eggs bathed in vinegar.
4. Procedure
Day 1- The eggs were removed from the vinegar bath and dried using paper towels. The eggs were measured around the horizontal middle and the weight was taken in grams. This data was recorded. The first egg was placed in a foam cup half filled with distilled water and the cup was labeled with a ‘W’ for water and a number ‘1’. The other egg was placed in a foam cup half full of corn syrup and the cup was labeled with a ‘CS’ for corn syrup and a number a ‘2’. The cups were moved to a lab station out of the way, the paper towels were thrown away and the tape measure was replaced.
Day 2- After the eggs were left in the cups for 72 hours they were removed and dried using paper towels. The eggs were again measured using the tape measure and the scale (in grams). Data was recorded and the paper towels as well as the cups were thrown away. The eggs were observed and observations were recorded. Then the eggs were also disposed of.
5. Data and Observations
The egg that was placed in the distilled water swelled slightly after twenty minutes in the cup. After 72 hours, however, the egg had a small hole in it and had returned to its original size. The egg that had been placed in corn syrup had shrunk and the shell was translucent in some places. There were dents in the shell and when rolled on a paper towel, the egg flattened slightly and left a chalky, yellowish- white residue on the paper towel.
Graph number one describes the size and appearance of the egg that had been in distilled water before and after the egg had been place in the water. Graph two describes the size and appearance of the egg that had been soaked in corn syrup both before and after it had been placed in the cup. Graph three represents the change in size of the eggs according to how long they were left in the corn syrup and water by the whole class. Each group (1-10) recorded the data on this graph.
6. Error Analysis
During the experiment, after the eggs had been placed in the cups and moved to the lab station, it was realized that the weight of the eggs before the experiment had not been taken. It was too late to measure the weight of the eggs. Next time, in order to make more accurate quantitative observations, we should pay more attention and be more aware of instructions.
7. Results
Egg Osmosis Lab Analysis Questions
1. When the egg was placed in the water, in which direction did the water molecules move? The polar water molecules moved from the hypotonic environment of the water through the egg shell into the egg.
2. On what evidence to you base this? Based this on the evidence that the egg was slightly larger than it began after soaking in the water, I concluded that some of the water must have moved through the semi permeable egg shell into the egg.
3. How do you explain the volume of liquid remaining when the egg was removed from the syrup? It appeared that there was more liquid in the cup but that the syrup was much thinner and seemed watered down. This may be because the water within the egg moved through the semi permeable egg shell out of the egg where there was a lower concentration of solvent and a higher concentration of solutes.
4. Why did the water molecules travel better inside the cell than the syrup molecules? The water molecules may have moved better inside the cell because the outermost layer of the semi permeable membrane has polarity. The water molecules are also polar which would mean the water would be attracted to the semi permeable membrane, and would pass through it. Also, the water molecules are much smaller than the particles that make up the syrup which makes it easier for them to pass through the membrane.
5. What is the purpose of placing the egg in the vinegar? The egg was placed in the slightly acidic vinegar so that it would eat away at the outermost layer of the calcium carbonate shell leaving only the cell membrane of the egg which is the part of the egg that we want to observe.
6. Did your results match the results found in the rest of the class? Why? Our eggs showed similar changes to those of the rest of the class. For the most parts, our results were more exaggerated because we left our eggs in the cups for a much longer amount of time (72 hours).
- Conclusion
The egg that had been placed in the cup of water swelled very slightly after soaking for 72 hours. This is because the concentration of solvent within the egg was much lower than the concentration outside the egg. The water molecules moved across the semi permeable egg membrane into the egg. The polar water molecules were attracted to the polar tops of the phospholipids that make up the plasma membrane. The egg that had been soaked in corn syrup shrunk quite a bit. This is because there was a higher concentration of solvent inside the egg cell. In my hypothesis, I stated that the egg that would be soaked in water would swell and that the egg in corn syrup would shrink and become more paper- like as well as thinner. My hypothesis was supported. What occurred in the cup of water was osmosis. Osmosis is the movement of water molecules across a semi permeable membrane from an area of higher concentration to an area of lower concentration. Osmosis also occurred in the corn syrup cup but the significance of the corn syrup was to represent selective permeability of the cell membrane as well as osmosis. It was visible that the water molecules from with in the egg cell were able to leave the cell through the cell membrane but the particles of corn syrup were unable to pass through the membrane into the cell.
I thought this lab was very effective and changes to the procedure might make it less so.