Deteremining The Effect Of Substances On Membrane Of A Cabbage Cell

by melisaturkay (student)

Table 1: Raw data collected for cabbage in different substances. With average pH obtained.

We observed that ethanol was slowest to break down the membrane of a cabbage cell, because when we came back to record down our results from the experiment, the color purple wasn’t fully diffused in side the test tube. Therefor unlike heated distalled water, hydrochloric acid (HCl) and sodium hydoxide (NaOH), the color wasn’t dispersed evenly. Also knowing that the cell membrane of cabbage was broken down in heated distalled water, HCl and NaOH, we checked for any shape change but there were no visible change.

Table 2: Raw data collected by Bolayır’s group on color change of cabbage in different substances with average pH obtained.

Discussion

As we conducted our experiment using heated distilled water, ethanol, HCl, NaOH, and distilled water we had the opportunity of observing how different substances with different properties and even under different conditions affected the membrane of a cell. Placing cabbage cells into distilled water and heated distilled water allowed us to make conclusions based on how temperature affects the structure of a membrane. Where distilled water had no affect on the membrane of a cell, heated distilled water oppositely broke down the cell membrane releasing chemicals which changed the color of the solution to dark purple. NaOH and HCl allowed us to make conclusions about how pH affected the membrane as well. NaOH being very basic with a pH of 1.5 as seen in Table 1, and HCl being very acidic again as written on Table 1, showed that very acidic, basic solutions had the ability of breaking down the membrane of a cell. Also since distilled water with a neutral pH had no affects on the cabbages membrane structure, we could conclude that increase/decrease in pH have a similar affect on the membrane of a cell. Lastly the testing of ethanol’s affect on the cell membrane gave us that the group alcohols were able to release pigments from the membrane, even though it happened at a slower rate.

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The reason why the darkest color was observed in the cabbages inside the heated distilled water was because the amount of pigments that went through the permeable membrane was the most. The reason behind why the membrane became more permeable with heated distilled water instead of distilled water at room temperature was because the structure of the cell membrane is formed by a phospholipid bilayer which is, a double layer of phospholipid molecules arranged with their hydrophobic fatty acid tails pointing inwards and protein molecules which are in the bilipid layer (Childs, 2001). Therefor the proteins in the phospholipid bilayer denature at high temperature, as all proteins do, and also it becomes more fluid. The e high temperature creates gaps appear on it, and the pigments are dissolved in the heated distilled water. Because of the gaps more pigment release, and more the membrane is broken down (Wise, 2004).

Besides temperature, pH affects membranes by affecting the proteins that make up the cell membrane as well. As mentioned previously nearly all cell membranes contain proteins which are made of amino-acids which contain Nitrogen, Oxygen and Hydrogen mainly. Therefor hydrogen bonds are created between the H and 0 atoms. When the pH of a solution changes, position of the hydrogen bonds change because H atoms tend to change place (White, 2004), because amino-acids are amphoteric change with pH which is acidic or basic by gaining H+ or OH-.

Lastly the experiment conducted using ethanol also showed a color change. Unlike how temperature and pH affected the phospholipid bilayer, ethanol affects the cells' osmotic environment. Because of its small structure ethanol can move through a permeable membrane easily. By entering the cell ethanol disrupts this flow. It changes the regular lining of water molecules inside the cells vacuole. This causes the cell to stretch and therefor have bigger holes, letting the pigment inside the cell travel out in to test tube quicker (Kinseth, 2006).

We compared results to other groups in our class such as Bolayır’s group, which the results are shown on Table 2. Accept their results for distilled water, which is a slightly purpleness in the test tube, their results support our results. Both color changes which are yellow for NaOH and pink/red for HCl correspond to each other. The reason for why our results varied is most likely because of the different pH levels we had for the distilled water. Because of different pH levels our hydrogen bond lining most likely differed slightly, which affected the amount of pigments inside the cell to be released.

We also had a few limitations. Through out the given period of time we were expected to conduct two different experiments, therefor we were limited to spending half of the class period for conducting this experiment and the rest for the second experiment. We were also limited with the diameter of the cabbages. Each cabbage leaf was approximately the same size, if we could have had smaller diameter the color obtained in the test tube would have been stronger. Lastly we were only limited with one cabbage, if we were able to conduct the same experiment using different cabbages we could of come up with more detailed observations.

In order to improve the experiment we could of used other solutions with a smaller range of pH in order to draw more detailed conclusions. Also another experiment could have been conducted for the temperatures affect on the membrane of the cabbage cell. With smaller and more intervals of temperature, we would have had more data providing us with what temperatures affected the membrane the most or the least.

Bibliography

Bolayır, M & Tuncel, I& Anna, Z & Volkova, M (2011). Deteremining the effect of substances on membrane of a cabbage cell, BLIS, Grade 11, Lab Report, Ankara, Turkey

Childs, G. V. (2001, October 07). Membrane structure and function. Retrieved from http://www.cytochemistry.net/cell-biology/membrane_intro.html

Kinseth, M. (2006, March 29). How does ethanol effect plasma membranes. Retrieved from http://www.madsci.org/posts/archives/2006-03/1143666101.Cb.r.html

White, I. (2004, March 25). Why and how do certain ph ranges effect the cell membrane. Retrieved from http://www.madsci.org/posts/archives/2004-03/1080223472.Cb.r.html

Wise, Y. (2004, January 29). Factors affecting cell membrane permeability. Retrieved from http://www.coursework.info/GCSE/Chemistry/Aqueous_Chemistry/Factors_affecting_cell_membrane_permeabi_L51402.html

Deteremining The Effect Of Substances On Membrane Of A Cabbage Cell

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