Introduction
Every cell is surrounded by a wall of protection known as a cell membrane or plasma membrane, it is really small and tiny to be seen by the naked eye, the cell membrane can only be seen by a light microscope. (Newton & Joyce, 2020). The Cell membrane is referred to as the ‘fluid mosaic model’ because of its fluidity / flexibility since it is made up of different parts to form one final product like a mosaic. (Hall, 2020). The Cell membrane consists of a lipid bilayer which is made up of phospholipid molecules, which has a head that is attracted to water and a tail that repels away from water, hydrophilic and hydrophobic, respectively, this makes the lipid bilayer. In between the layers of these phospholipid molecules are wedged cholesterol molecules which help with the movement of substances from one side to another. (Newton & Joyce, 2020), (Hall, 2020). Additionally, the proteins and carbohydrates are found around the holes and help move molecules in and out of the cell. There are also proteins attached to the inner and outer surfaces of the membrane.(Biology4Kids, 2020)
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A function of the cell membrane is to separate the cell contents from the extracellular environment, the cell membrane surrounds the cytoplasm of living cells, physically separating the intracellular components such as the Nucleus, endoplasmic reticulum, Golgi body and mitochondria, from the extracellular environment. The cell membrane also acts as a barrier, substances that enter / leave the cell must pass through the cell membrane. (Newton & Joyce, 2020). For example, channel proteins form a channel through the membrane and have a central pore that allows ion, water, and other small molecules to pass through. (Cooper GM. The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates; 2000. Transport of Small Molecules.) The main functions of the cell membrane; acts as a physical barrier, regulates the passage of materials, used for sensing or sensitivity and support. (Newton & Joyce, 2020)
For the cell to survive cellular transport is necessary, hence cell membranes are described as being differentially permeable (Semi-permeable or selectively permeable), meaning it only allows certain ions and molecules to pass through, but constrains others. (Newton & Joyce, 2020) Some transports are passive processes; meaning the cell’s energy, that comes from respiration, does not have to be used. Active processes require the cell’s energy for the transfer to occur. There are three basic processes for transporting materials; diffusion, carrier-mediated transport, vesicular transport. Osmosis is similar to diffusion, however this process is different, osmosis is when water passes through a differentially permeable membrane from a region of higher water concentration gradient to a region of lower water concentration gradient. (Newton & Joyce, 2020), (Hall, 2020).
Aim
The aim of the osmosis egg experiment and investigation is to clearly see what happens after osmosis and understand what osmosis actually is, under different conditions.
Hypothesis
EGG A: If Egg A is placed in salt crystals (High concentration condition), within the beaker, the intracellular fluid within the egg will undergo osmosis and transport the fluid to the extracellular environment, through the cell membrane, causing decrease in the weight of Egg A.
EGG B: If Egg B is placed in Distilled water (Normal Water Potential (or) Condition), within in the beaker, the intracellular fluid within the egg will undergo osmosis and either transport the extracellular fluid (distilled water) into the intracellular environment, through the cell membrane or (vice versa) causing increase in the weight of Egg B.
EGG C: If Egg C is placed in 0.1M of salt solution (High Concentration Solution), within the beaker, the intracellular fluid within the egg will undergo osmosis and transport the intracellular fluid to the extracellular environment, through the cell membrane, causing increase in the weight of Egg C.
EGG D: If Egg D is wrapped with plastic and placed within the beaker, the intracellular fluid will stay within the egg and will not undergo an osmosis process, causing the weight of Egg C to stay the same.
Materials
4 De-Shelled Eggs
250 Grams of Table salt
200 mL Distilled Water
200 mL O.1M Salt (NaCl) Solution
4*250ml Beaker Labelled A, B, C and D
Electronic Balance or Scale
Paper Towel
Camera
Method / Procedure
Weigh each egg and record its weight in the column headed starting weight of egg
Egg A – Place some salt crystals in the base of Beaker SA making a hollow in the middle
Place the egg into the hollow and cover it with more salt. Make sure none of the egg is showing above the salt.
Egg B – gently place the egg in beaker C and cover with distilled water
Egg C – gently place the egg in Beaker C and cover with 0.1M salt solution
Egg D – carefully wrap the egg in plastic wrap and place in Beaker D
Cover each beaker tightly with plastic wrap
Leave eggs overnight in a location where they will not be disturbed
Continuation of Method
Next lesson
Remove the eggs carefully from each of the treatments. Gently wash off the excess salt and dab the eggs with paper towel to remove excess water.
Re-weigh each of the eggs and record its weight in the table column headed ‘End Weight Of Egg’
Calculate the amount of water lost or gained by finding the weight difference between column 1 and column 2. Record the difference in the column 3 headed ‘Amount Of Water Lost (or) Gained’
Results
Within this table D.P. stands for Decimal Place
Treatment
Starting Weight of Egg
End Weight of egg
Amount of Water lost/gained
Percentage Weight Change
Egg in salt crystals
Observations:
86.6 Grams
Normal De-shelled Egg, Yolk is Visible
79.2 Grams
The Egg Yolk Was More Visible, the Egg lost weight
Egg Lost 7.4 Grams of Weight
7.4*100/86.6 =
8.5% (1DP)
Egg in distilled water
Observations:
78.4
Normal De-shelled Egg, Yolk is Visible
N/A-
Egg Automatically Busted overnight, in distilled water, making, the water look murky
N/A-
N/A-
Egg in 0.1 M salt solution
Observations:
65.7 Grams
Normal De-shelled Egg, Yolk is Visible
75.6 Grams
Could not see the Egg Yolk, The Egg gained weight
Egg Gained 9.9 Grams of Weight
9.9*100/65.7 =
15.0% (1DP)
Egg in Plastic wrap
Observations:
81.1 Grams
Normal De-Shelled Egg, Yolk is Visible
80.4 Grams
Not Much Change
The Egg Lost 0.7 Grams of Weight
0.7*100/81.1 =
10.9 % (1DP)
Discussion
Egg A:
The result of the osmosis experiment for Egg A, conveys that when Egg A was buried / placed in salt crystals the weight decreased from its initial weight (86.6 grams to 79.2 grams), overnight by 7.4 grams, percentage weight change of 8.5%, rounded to 1DP. This tells me that the salt crystals saturated the egg of its intracellular fluid. Moreover, the salt crystals can considered as the hypertonic solution, therefore, when the hypertonic solution saturated Egg A it means that the intracellular fluid (water) from the egg was transported outwards through osmosis, a process in which Egg A had more intracellular fluid than the extracellular environment, which was transported outwards from higher water concentration gradient (water from the intracellular environment of Egg A) to a region of lower water concentration gradient, (outside Egg A).
Egg B:
The result of the osmosis experiment for Egg B, illustrates that when Egg B, (lower concentration gradient) was in distilled water, (higher concentration gradient or solvent) Egg B bursted overnight, and made the water murky, this could be from, Egg B absorbing too much water from the process of osmosis, (change in the concentration gradient). this is just an inference, however, since the egg was bursted we cannot fully deduce that Egg B increased or decreased in weight, the initial weight was 78.4 grams. Thus, experimenting with Egg B could not be further applied to this investigation, and the egg had to be thrown out.
Egg C:
The result of the osmosis experiment for Egg C, shows that when Egg C, (lower concentration gradient) was placed in 0.1M of Salt Solution, (higher concentration gradient) the weight increased from its initial weight (65.7 grams to 75.6 grams), overnight by 9.9 grams, percentage weight change of 15.1%, rounded to 1DP. This tells me that the salt solution of 0.1M increased the concentration gradient of Egg C’s intracellular fluid. Furthermore, the 0.1M can be considered as the hypotonic solution, therefore, the hypotonic salt solution, (high concentration gradient) increased the low concentration gradient of Egg C, to a high concentration gradient, it means that some of the water or salt solution was transported into Egg C through the cell membrane, through the process of osmosis, a process in which Egg C had less intracellular fluid than the extracellular environment, which was then altered when the salt solution, (higher water concentration gradient) was transported inwards from the extracellular environment of Egg C to a region of lower water concentration gradient, (inside Egg C).
Egg D:
The result of the osmosis experiment for Egg D portrays that when Egg D was wrapped in plastic, (cling wrap) the weight decreased from its initial weight (81.1 grams to 80.4 grams), overnight by 0.7 grams, percentage weight change of 0.9% rounded to 1DP. This tells me that there wasn’t a huge effect of osmosis in Egg D, However the 0.7 grams that decreased could be due to evaporation, since we did leave our beakers on the window sill and therefore prolonged exposure to sunlight may have caused evaporation, hence the change of 0.7 grams.
Flaws
Some flaws that occurred during the investigation which altered the accuracy of the results and the overall investigation itself were; all beakers with eggs and solutions were left on window sill, thus sunlight could have increased the weight change, affecting our results, another flaw was that Egg B automatically bursted overnight which stopped our experimentation on Egg B which has been stated above, which has distorted the reliability of our results within this report about osmosis. Additionally, the materials section of the investigation has only said to be 4 de-shelled fresh eggs, however the type or brand of egg can also affect the results, for example, cage fresh eggs and free-range fresh eggs, because the weight of free-range eggs are heavier than cage fresh eggs.
Conclusion
The findings found in this experiment prove that osmosis has happened in this experiment in some Eggs, A and C. Osmosis can only happen when there is a low water concentration gradient which has to be balanced or taken care of by transporting substances from the high-water concentration gradient.
My Hypothesis for Egg (A); ‘If Egg A is placed in salt crystals (High concentration condition), within the beaker, the intracellular fluid within the egg will undergo osmosis and transport the fluid to the extracellular environment, through the cell membrane, causing decrease in the weight of Egg A.’
My Hypothesis was supported since there was a decrease in the weight of Egg A, when compared to the initial weight, (86.6 grams) and ending weight (79.2 grams) of Egg A, demonstrating that osmosis has occurred which is portrayed through the weight change.
My Hypothesis for Egg (B); ‘If Egg B is placed in Distilled water (Normal Water Potential (or) Condition), within in the beaker, the intracellular fluid within the egg will undergo osmosis and either transport the extracellular fluid (distilled water) into the intracellular environment, through the cell membrane or (vice versa) causing increase in the weight of Egg B.’
My Hypothesis cannot be proven for this Egg, because the Egg B bursted overnight while sitting in the solution therefore my hypothesis could not be tested.
My Hypothesis for Egg (C); ‘If Egg C is placed in 0.1M of salt solution (High Concentration Solution), within the beaker, the intracellular fluid within the egg will undergo osmosis and transport the intracellular fluid to the extracellular environment, through the cell membrane, causing increase in the weight of Egg C.’
My Hypothesis was supported because there was an increase in the weight of Egg C, when compared to the initial weight, (65.7 grams) and ending weight (75.6 grams) of Egg C, illustrating that osmosis has occurred, which is revealed through the weight change.
My Hypothesis for Egg (D); ‘If Egg D is wrapped with plastic and placed within the beaker, the intracellular fluid will stay within the egg and will not undergo an osmosis process, causing the weight of Egg D to stay the same.’
My hypothesis was not supported, when paralleled to the initial weight, (81.1 grams) and ending weight (80.4 grams) of Egg C, there has been a change of 0.7 grams, however the weight change cannot be by osmosis, because there was no solution to make the change.
References
Biology4Kids. (2020, February 27). Biology4kids.com. Retrieved from Biology4Kids: http://www.biology4kids.com/files/cell_membprot.html
Hall, M. I. (2020). Power Point Notes On Cells, Cell Membrane and Cell Structure. Perth: Isobel Hall.
Newton, T., & Joyce, A. (2020). Human Perspectives Units 1&2 ATAR 7th Edition. Perth: Nelson Netbook.
Cooper GM. The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates; 2000. Transport of Small Molecules.)
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