Osmosis Lab Report
Osmosis
The purpose of this lab is to study how membranes of plant and animal cells react when exposed to different solutions. The first experiment involves purple onion skin and the second involves rat blood in various solutions.
I needed to understand certain terms before preforming this lab to be able to efficiently explain what is happening to the cells. Diffusion is the tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area. Facilitated diffusion is the spontaneous passage of molecules and ions bound to a specific carrier protein across a biological membrane down their concentration gradient. Active transport is the movement of a substance across a biological membrane …show more content…
against its concentration or electrochemical gradient with the help of energy input and specific transport proteins. Osmosis is the diffusion of water across a selectively permeable membrane. A hypotonic solution is a solution with a lower solute concentration when comparing two solutions. An isotonic solution is a solution having the same solute concentration as another solute. A hypertonic solution is the solution with the greater solute concentration when comparing two solutions. A selectively permeable membrane is a property of biological membranes that allow some substances to cross more easily than others. A semi-permeable membrane is a membrane that will allow certain molecules or ions to pass through it by diffusion. I also gained a better understanding of the plasma membrane. “the plasma membrane functions as a selective barrier that allows sufficient passage of oxygen, nutrients and wastes to service the entire volume of the cells” (Campbelle & Reece,2005,p.99). The plasma membrane consists of two hydrophilic regions and a hydrophobic region. There are two layers of phospholipids with the phospholipid heads facing opposite directions, with the tails sandwiched between. The plasma membrane also contains proteins that are embedded within the membrane that help transfer compounds in and out of the cell. What is let in and out of the cell is specific to the types of proteins and phospholipids present in the membrane. Figure 1 shows the layout of the phospholipid bilayer.
Figure 1
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The question being asked by this lab is “How will a plant or animal cell react to different solutions?” My hypothesis is that the cell will remain stable when it is in a isotonic solution whether it is a plant or animal cell. When a cell is placed in a hypotonic solution, I expect for water to be absorbed faster than it is released and in a hypertonic solution, water will leave the cell faster than it can enter the cell. I have learned that this is a standard way a cell will react when placed in a solution. How plant or animal cells react will vary from solution to solution. In the first experiment, titled plasmolysis, I had to cut three very thin slices of a purple onion membrane. Each slice was placed on a separate microscope slide. A couple drops of water were placed on the first slice of onion. Another couple of drops of 0.3M sucrose solution were placed on the second slice of onion and finally a couple drops of 2.0M sucrose solution was place on the third slice of onion. I then observed each slide under a microscope of 10x power and drew what I observed.
In the second experiment, titled hemolysis, I obtained six test tubes and placed 2 mL of the following solutions into separate test tubes: water, glucose, glycerol, 0.3M sucrose, 2.0M sucrose and urea.
I then added two drops of rat blood to the first test tube and started the timer. I swirled the solution and placed an index card behind the test tube to see if I could observe the lines of the index card through the solution. If after two minutes I couldn’t see the lines, I moved on to the next test tube and added two drops of rat blood. The same protocol followed with the remaining solutions; if after two minutes the lines from the index card are not visible, move on to the next solution. I recorded the time it took to see the lines of the index card on the chart provided in the lab. If after 30 minutes and the lines of the index card were not visible, the records should state “no hemolysis”.
In the first experiment, I observed the onion membranes under a microscope when it was placed in different solutions. The first onion membrane I observed was placed in water. The cells looked swollen and tightly compacted. When I observed the onion skin in 0.3M sucrose, the cells were loosely compacted. I last observed the onion membrane in 2.0M sucrose and the cells looked very thin and far apart from each other in comparison to the other slides. Table 1 shows the data I
recorded.
Table 1 | | | 0.3M Sucrose H2O 2.0M Sucrose
Image provided by www.sorokaapbio1112.blogspot.com
In the second experiment, I was able to see the lines of the index card after two minutes with water and 0.3M of urea and after 30 minutes with 0.3M glycerol. I was not able to see the lines of the index card after the 30 minute time limit with 0.3M glucose, 0.3M sucrose and 2.0M sucrose. Table 2 shows the data I recorded from this experiment.
Table 2 Name of Compound | Concentration (M) | Time (min) | Water | - | 2 minutes | Glucose | 0.3 | No hemolysis | Glycerol | 0.3 | 30 minutes | Sucrose | 0.3 | No hemolysis | Sucrose | 2.0 | No hemolysis | Urea | 0.3 | 2 minutes |
In the first experiment water is hypotonic to the onion cell. The cells become turgid which is the normal state of a plant cell. A walled cell becomes turgid if it has a greater solute concentration than its surroundings, resulting in the entry of water. The water was absorbed by the plant cell making it look swollen. When the onion membrane was placed in 0.3M sucrose, the cell became flaccid, meaning limp. Water enters and exits the cells at the same rate. When the onion membrane is placed in 2.0M sucrose, you can see the plant cell membrane is detached from the plant cell wall. This is a hypertonic solution to the onion cell and the cell is plasmolysed. Plasmolysis is a phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall. The results of this experiment agree with my hypothesis in a isotonic solution the cell will remain stable or the same. When the cell is placed in a solution unlike itself, such as a hypertonic solution it will lose water or a hypotonic solution where the water concentration is higher outside of the cell and the cell will gain water. Other experiments that could be performed is using other solutions to find out what can be absorbed by the cell to discover what compounds can be found in plant cells.
In the second experiment I discovered that water and urea quickly cause hemolysis. Hemolysis is when a blood cell bursts. This happens in a hypotonic solution where water enters the cell faster than it exits. Hemolysis also occurs when the blood was placed in glycerol but it took a long time in comparison to urea and water. The compounds that caused no hemolysis were glucose, 0.3M sucrose, and 2.0M sucrose. These solutions probably caused no hemolysis because the molecules could either not pass through the membrane or the concentration of water was equal to that inside the blood cell. This experiment did not fully coincide with my hypothesis because in the 2.0M sucrose solution, the blood cells should have become shriveled; meaning the lines of the index card should have become visible after some time. The other compounds and cells reacted as my hypothesis stated they should. I would have liked to perform this experiment again ensuring that the right solutions were used. I would also like to conduct another experiment where I can rack how long it will take for the lines of the index card to become visible with no time limit. This experiment raised questions for me about what molecules can cross the membrane of blood cells. Observation of the blood cells in the solutions under a microscope would have helped a lot.
The purpose of this lab is to study how membranes of plant and animal cells react when exposed to different solutions. The first experiment involves purple onion skin and the second involves rat blood in various solutions.
I needed to understand certain terms before preforming this lab to be able to efficiently explain what is happening to the cells. Diffusion is the tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area. Facilitated diffusion is the spontaneous passage of molecules and ions bound to a specific carrier protein across a biological membrane down their concentration gradient. Active transport is the movement of a substance across a biological membrane …show more content…
against its concentration or electrochemical gradient with the help of energy input and specific transport proteins. Osmosis is the diffusion of water across a selectively permeable membrane. A hypotonic solution is a solution with a lower solute concentration when comparing two solutions. An isotonic solution is a solution having the same solute concentration as another solute. A hypertonic solution is the solution with the greater solute concentration when comparing two solutions. A selectively permeable membrane is a property of biological membranes that allow some substances to cross more easily than others. A semi-permeable membrane is a membrane that will allow certain molecules or ions to pass through it by diffusion. I also gained a better understanding of the plasma membrane. “the plasma membrane functions as a selective barrier that allows sufficient passage of oxygen, nutrients and wastes to service the entire volume of the cells” (Campbelle & Reece,2005,p.99). The plasma membrane consists of two hydrophilic regions and a hydrophobic region. There are two layers of phospholipids with the phospholipid heads facing opposite directions, with the tails sandwiched between. The plasma membrane also contains proteins that are embedded within the membrane that help transfer compounds in and out of the cell. What is let in and out of the cell is specific to the types of proteins and phospholipids present in the membrane. Figure 1 shows the layout of the phospholipid bilayer.
Figure 1
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The question being asked by this lab is “How will a plant or animal cell react to different solutions?” My hypothesis is that the cell will remain stable when it is in a isotonic solution whether it is a plant or animal cell. When a cell is placed in a hypotonic solution, I expect for water to be absorbed faster than it is released and in a hypertonic solution, water will leave the cell faster than it can enter the cell. I have learned that this is a standard way a cell will react when placed in a solution. How plant or animal cells react will vary from solution to solution. In the first experiment, titled plasmolysis, I had to cut three very thin slices of a purple onion membrane. Each slice was placed on a separate microscope slide. A couple drops of water were placed on the first slice of onion. Another couple of drops of 0.3M sucrose solution were placed on the second slice of onion and finally a couple drops of 2.0M sucrose solution was place on the third slice of onion. I then observed each slide under a microscope of 10x power and drew what I observed.
In the second experiment, titled hemolysis, I obtained six test tubes and placed 2 mL of the following solutions into separate test tubes: water, glucose, glycerol, 0.3M sucrose, 2.0M sucrose and urea.
I then added two drops of rat blood to the first test tube and started the timer. I swirled the solution and placed an index card behind the test tube to see if I could observe the lines of the index card through the solution. If after two minutes I couldn’t see the lines, I moved on to the next test tube and added two drops of rat blood. The same protocol followed with the remaining solutions; if after two minutes the lines from the index card are not visible, move on to the next solution. I recorded the time it took to see the lines of the index card on the chart provided in the lab. If after 30 minutes and the lines of the index card were not visible, the records should state “no hemolysis”.
In the first experiment, I observed the onion membranes under a microscope when it was placed in different solutions. The first onion membrane I observed was placed in water. The cells looked swollen and tightly compacted. When I observed the onion skin in 0.3M sucrose, the cells were loosely compacted. I last observed the onion membrane in 2.0M sucrose and the cells looked very thin and far apart from each other in comparison to the other slides. Table 1 shows the data I
recorded.
Table 1 | | | 0.3M Sucrose H2O 2.0M Sucrose
Image provided by www.sorokaapbio1112.blogspot.com
In the second experiment, I was able to see the lines of the index card after two minutes with water and 0.3M of urea and after 30 minutes with 0.3M glycerol. I was not able to see the lines of the index card after the 30 minute time limit with 0.3M glucose, 0.3M sucrose and 2.0M sucrose. Table 2 shows the data I recorded from this experiment.
Table 2 Name of Compound | Concentration (M) | Time (min) | Water | - | 2 minutes | Glucose | 0.3 | No hemolysis | Glycerol | 0.3 | 30 minutes | Sucrose | 0.3 | No hemolysis | Sucrose | 2.0 | No hemolysis | Urea | 0.3 | 2 minutes |
In the first experiment water is hypotonic to the onion cell. The cells become turgid which is the normal state of a plant cell. A walled cell becomes turgid if it has a greater solute concentration than its surroundings, resulting in the entry of water. The water was absorbed by the plant cell making it look swollen. When the onion membrane was placed in 0.3M sucrose, the cell became flaccid, meaning limp. Water enters and exits the cells at the same rate. When the onion membrane is placed in 2.0M sucrose, you can see the plant cell membrane is detached from the plant cell wall. This is a hypertonic solution to the onion cell and the cell is plasmolysed. Plasmolysis is a phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall. The results of this experiment agree with my hypothesis in a isotonic solution the cell will remain stable or the same. When the cell is placed in a solution unlike itself, such as a hypertonic solution it will lose water or a hypotonic solution where the water concentration is higher outside of the cell and the cell will gain water. Other experiments that could be performed is using other solutions to find out what can be absorbed by the cell to discover what compounds can be found in plant cells.
In the second experiment I discovered that water and urea quickly cause hemolysis. Hemolysis is when a blood cell bursts. This happens in a hypotonic solution where water enters the cell faster than it exits. Hemolysis also occurs when the blood was placed in glycerol but it took a long time in comparison to urea and water. The compounds that caused no hemolysis were glucose, 0.3M sucrose, and 2.0M sucrose. These solutions probably caused no hemolysis because the molecules could either not pass through the membrane or the concentration of water was equal to that inside the blood cell. This experiment did not fully coincide with my hypothesis because in the 2.0M sucrose solution, the blood cells should have become shriveled; meaning the lines of the index card should have become visible after some time. The other compounds and cells reacted as my hypothesis stated they should. I would have liked to perform this experiment again ensuring that the right solutions were used. I would also like to conduct another experiment where I can rack how long it will take for the lines of the index card to become visible with no time limit. This experiment raised questions for me about what molecules can cross the membrane of blood cells. Observation of the blood cells in the solutions under a microscope would have helped a lot.