Permeability of Plasma Membranes

Permeability of Plasma Membranes ledger entryPlasma tissue layers be bi-layered tissue layers made up of amphiphillic molecules (having charged polar heads attending to be hydrophillic and uncharged fatty acid tails tending to be hydrophobic) that selectively allow entrance of certain commodious molecules into the mobile phones cytosol and through which weewee and small non-polar molecules may freely diffuse.This look into visualizeks to transform limited aspects of the permeability of the plasma tissue layer using the pondweed flip over membrane as model organism. Some of the factors upon which permeability of the plasma membranes of biological organisms depend argon differences in pH on opposite sides of the membrane, temperature, os submarine sandwichity, expression of certain membrane receptors and the concentration gradients of various molecules.This experiment is very limited in rise up and seeks to answer lonesome(prenominal) the question of what is the time depe ndence for permeability of glycerine through the cell membrane. Other experiments obtain answered many of our questions regarding this and have resulted in mathematical equations describing these results. This experiment give use one of the formula derived from these prior experiments, the EtherWater partition coefficient for alcoholsiii as a means of hypothesizing what the moment of this present experiment will be.I have hypothesized that within seconds of movie to a 0.3M (molar) hyper-tonic dissolver of glycerol, dissolved in an isosmotic deionized water (dH2O)/ sucrose antecedent, the ditchmoss foliation will plasmolyze irreversibly-an assumption I believe is support by the fact that glycerols etherwater partition coefficient is single 0.00066iii. pull ahead support for this supposition is the fact that glycerol has a relatively capacious chemical structureviii-owing to its three large, highly polar hydroxyl groups-and a large molecular weight of 92.0938 grams per mo le. Alternatively, it may be hypothesized that the glycerol-being an aliphatic alcohol (see plat in part IV(i) infra) which, itself makes up a part of the plasma membranevi-will be capable of more easily diffusing across the plasma membrane as compared to the sucrose, which cannot diffuse across the membrane, in which case not only will in that location be no severe plasmolysis unless there may, instead, be a build up of turgor pressure inside the cell due to the inward movement of the alcohol and its confinement in the central vacuole.MethodsIn order to discover what molar concentration of sucrose will be postulate in an aqueous effect to create a solution that is isotonic to the flip overs cytosol I shall perform a bifurcated experiment in which the first part shall be to determine this concentration. Part cardinal of this experiment will be to determine the period of time it takes for glycerol to diffuse across the plasma membrane.In order to determine which molar solutio n of sucrose is isotonic to the cytosol of the Elodea cell I de scarate 6 micro-centrifuge pipeworks with the markings 0.2M, 0.3M, 0.4M, 0.5M, 0.6M and isotonic respectively and using an adjus fudge pipette set 1000 L of premixed sucrose solution of distributively(prenominal) of the indicated molarities into the respective tubes. In each of these tubes I placed an Elodea flip and allowed them to sit for some tail fin legal proceeding my reflexions of plasmolysis along with depictiongraphs of leaves in similar states to what I ascertained are provided in give in 2 of the Table of observations of plasmolysis and photographs 2-6 in the Photograph table which can be found in sections III(A) (B) respectively. spot awaiting the leaves to finish soaking I viewed a dry mounted Elodea leaf under a microsocpe using 20X and 40X objectives with 10X ocular so as to have a better idea of what a normal Elodea leaf looks like for comparison to the viewing of the wet mounts photo of a l eaf in similar state to what I take noted is provided as photo 1 in the Photograph table of section III(B). I thus labeled 6 microscope dislocates using the comparable concentrations I apply when labeling the micro-centrifuge tubes. later on five minutes I prepared an individual wet mount of an Elodea leaf by placing a leaf from a micro-centrifuge tube onto a microscope glide, bearing its respective molarity, with the upper sur deliver of the leaf face up. I placed a cover slip over the leaf and gently tapped the cover slip so as to seat it onto the slide and to remove any excess solution. I whence viewed the wet mount-searching for indications of plasmolysis-under a microscope using the same 20X and 40X objective lenses and the 10X ocular lens I had viewed the dry mount and enter my observations then repeated this process for each of the leaves in the remaining tubes.I was unable to obtain photos of my observations but I have included photos downloaded from the internet whi ch were similar to what I had observed and provided them in tables 1-6 of section III(B).Having established which molarity of sucrose solution was isotonic with the cytosol of the cell (see table in section III(A)) I channelized the quantities of sucrose, glycerol (test solution) and 1-Propanol (counter test solution) I would need for the second part of this study. In those calculations I used the entropy presented in table 1 below. My calculations are presented in the Table of Calculations, table 3 of section III(C) infra.I plugged the results I obtained from table 3 into the formula C1 x V1 = C2 x V2 so that I may calculate the volumetrical quantity of each of these chemicals I would need to add to each of my 2 1 x 103 L test solutions, my calculations for each may be found in Table 4 of section III(C).victimization those calculation I then added the quantities of sucrose to each of the other two chemicals and subtracted the sum from the final volume of solution (1000 L) I wou ld be creating so that I will know the volume of deionized water (dH2O) I would need. Those calculations are shown in table 5 of section III(C).Using these calculations I then prepared 5 new micro-centrifuge tubes as follows 3 tubes each containing a 1000 L isotonic (0.4M) sucrose solution (one of which is to be used as a shun control) the fourth containing an aqueous solution of isotonic (0.4M) sucrose and 0.3M glycerol mixtures and the fifth containing an aqueous solution of isotonic (0.4M) sucrose and 0.3M 1-Propanol mixtures (counter control). I placed one Elodea leaf into each of the 3 isotonic solutions and allowed them to soak for well-nigh five minutes. After five minutes I prepared a wet mount of the first of the 3 leaves as previously described. After viewing the first leaf (the negative control) I placed the second leaf on a slide and added 2 drops of the 0.3M glycerol/ sucrose solution to the slide then viewed and put down my observations. I then prepared the third lea f using 2 drops of the 0.3M glycerol/Sucrose solution and viewed to be certain I obtained the same result as the last slide then after approximately 30 seconds added 2 drops of 1-Propanol/Sucrose solution (the counter test solution) to see if this would have an effect opposing that of the glycerol/Sucrose solution and recorded my observations which I describe next.ResultsA. Table of observations of PlasmolysisTable 2 Plasmolysis observations within five minutes of Elodeausing different sucrose solutions.Sucrose concentrationsPlasmolysis observed (Y/N)Sucrose concentrationsPlasmolysis observed (Y/N)B. Photograph tables (Photographs of Elodea leaves in various solutions)1. Normal leaf(similar observation as prior to placing in solution)2. Hypo-tonic solution(similar to observation as seen in 3. Isotonic solution(similar observation as in the isotonic solution and the 0.4M-0.5M sucrose solutions)4. Hyper-tonic solution(similar observation as seen in the 0.6M sucrose solution)5. Plasmol ysed leaf(similar observation as would have been seen in hyper-tonic solutions)6. Plasmolysis Recovery(did not observe any recovery events but this is what I would also have been sounding for had plasmolysis recovery taken place)C. Tables of CalculationsTable 3 Calculations for concentration of 0.3M glycerol/Sucrose solution.Amount of sucrose needed.137g x V = 0.4M x .001 LV = (.0004g/L) / (0.137g) = 0.002919 L or 2.91 x 103mLAmount of glycerol needed0.028g x V = 0.3M x .001 LV = (.0003g/L) / (0.028g) = 0.01071 L or 10.7 x 103mLAmount of 1-Propanol needed0.018g x V = 0.3M x .001 LV = (.0003g/L) / (0.018g) = .01667 L or 16.7 x 103mLTable 4 Calculations of volumetric quantities of each chemical needed to make 1000 L of each solution.2.92 L sucrose+ 10.7 L glycerol + x(dH2O) = 1000 L13.62 L + x(dH2O) = 1000 Lx(dH2O) = 1000 L 13.62 Lx(dH2O) = 986.38 L2.92 Lsucrose + 16.7 L 1-Propanol + x(dH2O) = 1000 L19.62 L + x(dH2O) = 1000 Lx(dH2O) = 1000 L 19.62 Lx(dH2O) = 980.38 LTable 5 Calcula tions of amounts to add to each solution. treatmentAt first viewing I did not quite understand what was happening as I had not previously seen an Elodea leaf that presented with protrude its large central vacuole let alone one that presented with chlorophyll end-to-end the entire cytosolic space. Having consulted with my fellow researchers (one of which obtained findings similar to mine in her experiment), none of whom had explanations for this result, I shall instead provide a summary of what I observed and what I had expected to observe.I had expected my first hypothesis to be borne out regarding the outward movement of water across the membrane and toward the hyper-tonic glycerol solution providing a sighting as in photograph 5, however what I discovered was an Elodea leaf showing absolutely no sign of plasmolysis. Instead of the expected I saw what was a leaf that appeared to be in a state of iso-osmolarity with its environment which would have been expected only in an isotonic solution as in photograph 3. There, also, was no turgor pressure as would have been seen in photograph 2 had the choice hypothesis of inward movement of glycerol across the plasma membrane been borne out.Finally, had there been a plasmolysed cell the addition of the counter test solution of 1-propanol should have caused recovery as seen in photograph 6 but being I was unable to obtain a plasmolysed cell I was also unable to observe recovery of such cell.The results of this experiment has go forth me unable to either accept or reject either of the two hypotheses provided above.