Throughout this experiment process, I discovered how to conduct tests on dialysis cells and record the data. I also learned how to weigh them, change the variables, and graph them. While conducting this experiment, I hypothesized that changing water temperature that the dialysis tubing soaked in would also change the weight of the cells. The methodology used included; soaking the tubing in water in order to get the open, filling them with either DI water or multose, sealing them with orange clips to prevent leakage, weighing the cells before soaking them as well as every 10 minutes, and submerging them in water of two separate temperatures. The results were as assumed, one of the temperatures produced heavier cells than the other.
The transfer of molecules across the membrane of a cell has been observed and simulated over a number of years. Recently it has been observed of how the two main process’, diffusion and osmosis, have become an important part of the life activity in organisms. Our lab was used as a similar simulation for the students to create and experiment with artificial cells by using dialysis tubing and observing the results of different solutes being transferred between environments.
The solutions we manipulated consisted of normal water and two separate solutions of 30% sucrose. The dialysis tubing was first set in H2O in order to allow easy prying and opening of the walls. Once the walls had been separated, one end was sealed by folding the tubing and clamping with the provided orange clips. 10 mL of the three different solutions went into the three different artificial cells . Our group released excess air by squeezing the tubing walls and refolding and clamping the unsealed end. This gave a complete artificial cell. Each cell was wiped dry with paper towel to remove excess water and weighed on the scale prior to step two.
Three 250 mL beakers and a temperature gauge were used for step two. The beakers just received just enough water to completely submerge one cell. The temperature of the water was measured and recorded in our table along with the preweights of the three artificial cell samples. The soaking stage was completed over a course of 90 minutes, with the weight of each tube being measured in 10 minute intervals. The breaks between each trial allowed our group to redry the tubes in order to get rid of excess water, and have the cells reweighed more accurately. Over the course of 90 minutes, the cells were checked a total of 9 times. When the 90 minutes were up and measurements were completed, cell and beaker solutions were poured down the drain while the artificial membranes were disposed of.
The weights plotted in the data table for the 30% multose showed results of increasing values every 10 minutes. This is the expected result of a hypertonic solution. Since the solute is less concentrated outside the artificial cell, additional water molecules tend to move in through the cell membrane until there is an equilibrium reached. This then caused the cell to swell and to increase in weight. This validated our groups hypothesis that the cell would have an increased weighted value as compared to the water-water cell solution. While the weight of the water-water trial did increase as well, we also expected this due to the imbalance of H2O molecules between environments.
While our hypothesis had proved to be valid, that soaking the cells in water for an allotted amount of time would result in a slight weight difference, there were some slight errors that followed our data. One included, having one time trial that decreased in rate rather than the expected increase. Flaws like this can be linked to ideas such as the cell being insufficiently soaked in the water, or that water had not been completely taken from all other trials which resulted in all weights being greater than this one. Our group concluded there was a small possibility of error resulting naturally from that the sucrose solution may have had an insufficient diffusion trial that therefore accounts for the shortage of water weight we expected to see. Overall, the data our group collected showed to be accurate and within good standing.
The article written by McCutcheon and Lucke, had some relevance to the hypothesis that my group created. Two passages from this article discussed the points that temperature would change the salt and essentially the volume,
“ 4. The initial rate of passage of the salt through collodion is greater the higher the temperature, but the rate is practically the same for all temperatures at the end of 30 minutes of dialysis. 5. The reasons for the results obtained in the experiment on pyridine are discussed from the viewpoint of the theory that water is an equilibrium mixture of hydrol (H20) and its polymers.” (McCutcheon & Lucke, 1926).
Another article written in 2004 by Wei-Mon Yan, Falin Chen, Hung-Yi Wu, Chyi-Yeou Soong, and Hsin-Shen Chu; Analysis of thermal and water management with temperature-dependent diffusion effects in membrane of proton exchange membrane fuel cells, also discusses content similar to my hypothesis,
Soowhan Kim and M.M. Mench also wrote a journal that discusses things similar to my hypothesis,
“When a membrane separates liquid water with different temperatures, water flows from hot to cold direction or vice versa, a process known as thermo-osmosis. The direction of water flow depends on the entropy difference between water in the membrane and external to the membrane; for example, water in a hydrophilic membrane can be considered to have a relatively ordered state compared to water existing outside the membrane.” (Kim & Mench, 2008).
Ralph N. Traxler also discusses similar concepts in his journal,
“It is a commonly recognized fact that rise in temperature causes a marked increase in the rate of osmosis and dialysis and also increases the osmotic pressure developed by a solution separated from the pure solvent by a semipermeable membrane.” (Traxler, 1927).
Each of the sources and quotes mentioned somewhat support the idea that the salt content can change when exposed to temperature, making my hypothesis true to an extent and deemed possible.
During one of our previous lab sessions, my group and I conducted an experiment that observed the change in weight of tubes containing thirty percent multose and water in different temperature settings. Before beginning this experiment, my group hypothesized that; as the maltose and water tubes sit in water of two different temperatures, they will both get increasingly heavier after each ten minute weighing period. We believed that the results would weigh more than when we did the experiment with sucrose and that one temperature would cause the tubes to weigh more than the other.
The variables used for this experiment were two dialysis tubes containing water, four tubes containing thirty percent maltose, and two temperature chambers filled with water and set to thirty degrees celsius and fifty degrees celsius. The tubes were soaked in water to soften them so that they could be opened and filled with the liquids. They were then clipped with orange clips to prevent water from exiting during the soaking and the water they were sitting in from entering. Each tube was filled using a 10mL cylinder to ensure that they all received equal amounts. Air was then squeezed out of the tube right before clamping the ends with the orange cell. Before placing the tubes inside the temperature chambers, they were blotted with paper towel to remove excess water from the outside and pre weighed.
The equipment that was used for the soaking steps included, three 250mL beakers and a temperature gauge. All three beakers were filled with enough water to cover the cells. Two beakers had also been placed in the temperature chamber prior to the testing so that they would match the conditions inside. The most important part of our soaking stage consisted placing two of the maltose and one of the water cells each in the two separate temperature chambers. From there, this experiment took place over a ninety minute period. The cells sat in the chamber for ten minutes before being removed and measured on the scale for change. This step was repeated every ten minutes until our time was up and we had nine different weights to record in our table for each cell. After this time period, the water and maltose was poured down the drains and the dialysis tubes were thrown away.
As it turns out our results were very similar for both temperatures used; thirty degrees celsius and fifty degrees celsius. The thirty percent maltose had similar weights in both and stayed between seventeen to twenty six grams throughout the experiment. While it made it easier throughout the experiment to predict the numbers, it was also hard to make sense of why this was happening. Also, during the experiment one of the tubes had either not been sealed properly or had some kind of hole in it. Throughout the experiment, this tube increasingly lost weight and fluctuated between eight and nine grams. This was different from our hypothesis since we did not predict that this would happen nor expect it.
After the experiment was completed, we conducted that the results we conducted over this time period were overall similar to what we had hypothesized. Due to increasing concentration of the solutes that were present, it was obvious that the weights of the results would be a higher value than the original. As seen on the graph pasted below, the weights did in fact increase, but at times they increased which seemed a little odd to us. While it seemed odd, most of the results still remained close to each other and still were similar to the hypothesis. So, although some error such as a leaking cell, possible incomplete submersion during soaking, or miss weighing might have taken place during the recording of the results, our results for our hypothesis still proved to be accurate and within a value that seemed reasonable.