Iycee Charles de Gaulle Summary Selective permeable membranes Essay

Selective permeable membranes Essay


This practical was to look into the effects of temperature on the selective permeable membranes of ruddy chou.


As Allaby ( 1999 ) said, the permeable membrane is a membrane that can choose the transition of certain substances in and out of cells based on the size and utility of molecules. For case, H2O and ions can go through in and out by simple osmosis diffusion ( high to low concentration ) , but some supermolecules like pigments can non. Inside the construction of the cell membrane, there are many different types of protein to choose and let some supermolecules to acquire through ( Peter, 2003 ) .

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The selectivity of these proteins is decided by the constructions themselves. Therefore, the cell membrane can maintain back uping some supermolecules inside the cell.The construction of protein can be affected by physical causes, such as high temperature. This procedure is called the denaturation of protein. Harmonizing to Charles ( 2003 ) , the protein construction turns into a random form after denaturation, and the belongingss of protein would be lost for good.

When the permeableness of the cell is changed, those supermolecules will be transported by diffusion, ( Wurts, 1987 ) because the concentration of pigment inside the cell is much higher than the environment. As a method, the consequence of different temperatures on the permeable membrane of ruddy chou can be determined by detecting the coloring material of the environment liquid.The pigment indoors ruddy chou is anthocyanin ( Dr. Stephen, 2009 ) . Harmonizing to The President and Fellows of Harvard College ( 2008 ) , it is soluble in vacuole and can reflect the pink-red coloring material of most ruddy fruits. Anthocyanin has a molecule of glucose and four aldehyde groups as map groups ( seeing figure 1 from The President and Fellows of Harvard College, 2008 ) .

Stairss ( from Second Biology Practical IFY Class Handout, Lane, R. 2009 )This practical was done follow harmonizing to the stairss. First, a cork bore bit was used to cut phonograph record of fresh ruddy chou into 42 pieces and each 3mm diameter phonograph record. All the phonograph record were placed in a little beaker and washed under running H2O for 5 proceedingss. Meanwhile, the trial tubing was labeled 30? , 40? , 50? , 60? , 70? , 80? and 88? , and a cylinder was used to add about 6cm3cold H2O to each. Third, a H2O bath utilizing a big beaker, tripod and gauze, and a intoxicant burner was prepared.

When the H2O was been heating, 6 ruddy chou phonograph record were impaled on a mounted acerate leaf and placed into the trial tubing labeled 30? . Equally shortly as the H2O was 30? , the burner was removed and the trial tubing was placed in the big beaker for precisely one minute. Then, the trial tubing was taken out and cooled down. The H2O was so heated to 40? and the same stairss for 30? were repeated. However, when the H2O was heated to 50? , the burner was removed and the 6 ruddy chou phonograph record on a mounted acerate leaf for 50? were placed into the H2O for precisely one minute.

Then the phonograph record were pushed off and set into the trial tubing labeled 50? to chill down. All the stairss for 50? were done exactly for the temperatures on 60? , 70? and 88? . Finally, after the phonograph record were left in the trial tubing for at least 20 proceedingss, the tubings were shaken and held to the white paper to compare the coloring material of each tubing.


The consequences of this practical were shown in Figure 2.In the first trial tubing, there are four phonograph record floated on the surface while three phonograph records in the following two tubings. The 1 for 60? was holding two phonograph record and more H2O than other. Colour changed seemingly in the left three tubings.

The phonograph record were droping and color changed into violet.


During this practical, many mistakes occurred. When the portion of 30? and 40? was being done, the 6 ruddy chou phonograph record were placed into the trial tubing so a tubing was placed into the big beaker. By making this incorrect measure, the temperature of H2O environment that the phonograph record experienced was likely lower than the coveted one, and it took clip for the cold H2O in the tubing.

Low temperature affected the consequences in the first two tubings. Another mistake was made by non utilizing pipette to mensurate the volume of H2O in each tubing. In fact, a calibrated pipette was provided. It is much more accurate than a measuring cylinder. This mistake affected all trial tubings for approximately 10 % . The volume of H2O in the 60? tubing was more than others.

It led to the coloring material of the liquid being lighter than expected. To better this, the calibrated pipette should be used to avoid this as instructed. The consequences can non be compared with the accomplished concentrations.Mentioning to the debut, the coloring material became more evident. The colourless observed in the first three tubings ( 30? – 50? ) shows that the temperature was non high plenty to denature the proteins in the selectively permeable membrane. The violet liquid in the last three tubings indicate that the permeableness of membrane was increased by the denaturation of protein which led to the let go ofing anthocyanin. It is because that the pigment concentration in H2O and cell doing the pigment to spread into H2O.Another phenomenon which is deserving sing is that merely some phonograph record in the first four tubing floated.

It is possible that high temperature did non merely denature the protein besides destroyed the construction of phonograph record. It is possible that the high temperature affected both on the construction of membrane and the equilibrium of diffusion of anthocyanin.


The consequences showed that the permeableness of selectively permeable membrane of ruddy chou additions with the higher temperature ( 70? – 88? ) and those discs became violet.


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    elmhurst.edu/~chm/vchembook/568denaturation.html [ Accessed clip: 01-03-2010 ]

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