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We therefore concluded that only small molecules like glucose and iodine can permeate through the bag, starch is too large. Introduction This lab has several key objectives. First, to learn about diffusion and osmosis, and the different factors that affect the rate at which these processes take place. In order for cells to maintain a stable state, they must be able to regulate the particles that move through the cytoplasm, and across its membranes. Diffusion and osmosis are the two physical processes that insure these things take place for the cells to operate smoothly.
Second, to gain a better understanding of he role of selectively permeable membranes in osmosis, and to learn about the significance of hypotonic, isotonic, or hypersonic solutions in relation. It is even possible to reversing osmosis! This process is used as method of water purification because it enables salt and wastes to be permeated out of the fresh water (Ginsberg, Middlebrows, 1986). Most importantly, the purpose of this lab was to learn to apply these concepts to the cellular and environmental levels that we encounter in everyday life.
Here are the specific points to each experiment. The purpose of this experiment was to observe the carmine particles in motion in order to gain a better understanding of the Brownian movement and the role of kinetic energy in diffusion. Brownian motion and diffusion can play a major role in the transportation of different particles in many different cellular processes. One example is that diffusion carries acting monomers to the site where they polymeric into F-acting- the framework for the cytokines in plants and animals! (Asks 1989). B.
Potato Core experiment The purpose of this experiment was to try to estimate the similarity of the potato tuber tissue after submersing it in a series of sucrose solutions with different molarities. The solution in which the incubated potato has the smallest change in weight will be approximately equal to the similarity of the potato. We hypothesized that the similarity of the potato would be 0. MM. Based on this hypothesis, we predicted that if the similarity of the potato were 0. 3, then the percent weight change would be (almost) zero.
Cells are primarily composed of water, and are termed selectively permeable since they allow water to move freely through the cytoplasm, but block the flow of macromolecules (Morgan, Carter 2005). Osmosis is the diffusion of water through a selectively permeable membrane from an area of low solute/high water concentration (hypotonic) to an area of high solute/low water concentration (hypersonic). Osmotic pressure is the force that can be applied to prevent water from flowing in this fashion (Morgan, Carter 2005).
A thorough understanding of these concepts is crucial in the medical field because all intravenous solutions administered to a patient must be isotonic, or have the same osmotic pressure as those of bodily fluids. (Trot 2008). If a certain solution or medication administered was hypotonic to the patient’s body fluids, too much water would flow into the cells, which would cause them o burst or undergo Allis. Likewise, if a patient is given a hypersonic IV, the cells would shrink (create) because water would flow out of the cell. (Trot, 2008).
Figure 1 shows this concept applied to red blood cells. Solute concentration is also important for the survival of plants. If plant cells lost too much water, they would die. This is why salting fields was a common, devastating war tactic because it would kill the crops in the field and create major food shortages! (The Biology Corner). Figure 1. Red Blood Cells in different concentrations of solutions. The purpose of this experiment was to simulate the permeability of cell membranes to glucose, starch, and iodine using dialysis tubing.
Using the Iodine test we were able to detect the presence of starch, and Benedicts reagent denoted the presence of glucose. We knew that the dialysis bag would allow some small substances to pass through it, but stop the larger molecules. Therefore, we hypothesized that glucose and starch would be able to pass through the dialysis bag, but that iodine would be too large to permeate through. We based our prediction on our hypothesis as follows: If glucose and starch can pass through the dialysis tubing, then the contents in the beaker will turn black ND Benedicts test will be positive outside the bag.
Materials ; Methods A. Plant and Animal Cell Diffusion and Osmosis (Morgan, Carter 2010) First, we examined the particles of carmine powder in an effort to better understand the Brownian movement, and the effect that the motion of the particles has on diffusion . Our class split up into groups of two; my partner set up the compound light microscope, while I prepared the carmine slide. We then observed the movement of carmine particles under the microscope, first with low power, and then on high power, and recorded the results. B. Potato Core Experiment (Morgan, carter 201 0)
First, we estimated the similarity of potato tuber cells by measuring the change in the potato’s’ weight after they were incubated in various concentrations of sucrose solutions (0. 1, 0. 2, 0. 3, 0. 4, 0. 5, 0. 6 M). First, we obtained mall of distilled water, and mall of each sucrose solution-which we placed in separate mall beakers. We then used a cork borer to extract 7 cylinders of potato. We then cut them all to about 5 CM long, and removed the skin from the ends. We placed all seven potato samples in a covered Petri dish so they would not dry out.
For consistency, we assigned each person their own, separate task to reform to each potato cylinder. First, one person removed the potato cylinder from the Petri dish and used a paper towel to blot. Then another person placed the potato on aluminum foil on the balance, weighed to the nearest 0. 01 grams, and recorded our results. Next, another group member cut the cylinder in half vertically and placed the pieces into the water beaker (recording the time). We then repeated the previous steps with the remaining potato cylinders, placing each one in separate beakers containing the various molarities of sucrose solutions.
We let each sample incubate for about 1. To 2 hours, swirling each beaker every 10 to 15 minutes. At the end of the incubation, we removed the potato samples, and recorded the time. Starting with the first sample, we removed the potato pieces and blotted with a paper towel to remove any excess solution. We then reweighed the potato pieces and recorded the final weight. We repeated this procedure with all of the remaining samples in the order in which they were initially placed in the solutions and recorded the results. C.
Dialysis Tubing Experiment (Morgan, Carter 2010) We tested the permeability of dialysis tubing to starch and glucose using the iodine test and Benedicts test . First, my partner and I prepared the dialysis bag by folding over CM of the tubing after it had soaked in water for a few minutes, and then closed the top off with a rubber band. We then opened the opposite end of the bag, and added approximately ml (4 pipettes full) of 30% glucose solution. We then added the same amount of starch solution. Next, we held the bag closed and thoroughly mixed the contents, and then recorded the color.
Next, we rinsed the outside of the bag with water. We then added mall of water to a mall beaker, and added a generous amount of iodine solution to the eater until it turned a yellow/amber color (and recorded the color). Next, we placed the bag into the beaker with water for 30 minutes, allowing the untied end to hang over the edge of the beaker. After about 30 minutes, we took the bag out and let it sit for another 30 minutes in an empty, dry beaker, and recorded the color of the solution in the bag and in the beaker. Next, we tested for the presence of reducing sugars using Benedicts test.
We labeled 3 test tubes: bag, beaker, and control. We put 2 pipettes of the bag solution into the bag tube, 2 pipettes of the beaker solution into the beaker tube, and pipettes of water into the water tube. We then added 1 full dropper of Benedicts reagent to each tube, placed the tubes in a boiling water bath for about 3 minutes, and then recorded our results Results In the first experiment, we examined carmine powder to become more familiar with the Brownian movement by observing particles in motion, and examined various factors that influence diffusion rates.
With the microscope on high power, it was apparent that the carmine particles moved around randomly and continuously. It also seemed as though the smaller particles moved at a more rapid rate than the larger particles. B. Potato Core Experiment We placed the potato cores in cups containing different concentrations of sucrose solutions to find out if the potato would gain or loose weight. When the potato was placed in cups containing sucrose molarities of 0. 0-0. 3, the potato gained weight. When placed in sucrose molarities of 0. 5 and 0. 6, the potato lost weight.