Apparatus and materials: 1 tube mouth rinse(4 brands), 3 cylinders beetroot, 1 pc razor blade, 1 pc white tile, 10 pcs test tubes, 2 pcs test tube racks , 1pc 10-mL measuring cylinder, 5 pcs labels , 1 pc forceps, 1 pc 500-mL beaker Aim : To study the effect of different brands of mouth rinse on the permeability of the membranes of beetroot tissue Problem: To compare the denaturation of membrane of cells in the effect of mouth rinse of different brands and find out which brand of mouth rinse damages the membrane of cells most. Therefore , the health risk of mouth rinse can be known. enaturation is used to describe protein only, not a membrane. –> destruction Hypothesis: The pigment in beetroot is permeable to the chemicals in the mouth rinse Principles: The plasma membrane is made up of protein and lipid molecules. These two main components are affected by various chemicals. In this investigation, we study the degree of denaturation of the membrane of beetroot by different substances. Beetroot cells contain a water-soluble pigment, , in their vacuole which upon denaturation of membranes is released into the surrounding medium.
When the beetroot discs are put into the mouth rinse and anthocyanin leaks out, the chemicals in mouth rinse are lipid-soluble molecules. The higher the concentration of the solvent, the more permeable the membrane will be. More anthocyanin from the beetroot discs will leak out. be careful, solvent does not have a “conc. ” Principle of design: The contents of lipid-soluble substances in of mouth rinse are to be determined and compared. Four different brands of mouth rinse are bought and used for comparison. The amount of anthocyanin given out can be observed and compared after immersing into mouth rinse.
Study the colour intensity find out the one contains the most lipid- soluble substances. The red pigment will leak to the surrounding solution by diffusion. Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration until the particles are evenly distributed. by reading the info on the label of ingredients? Independent variable is different brands of mouth rinse. Dependent variable is the amount of beetroot pigment leak out in the mouth rinse during experiment( colour intensity of the solution).
Controlled variables are number of beetroot discs, surface ?? of beetroot discs (Do you mean “size”? ), volume of mouth rinse, temperature, light intensity (what for?? ), the time used in doing the experiment (time for immersion?? ), the way performing the test with each brand of mouth rinse. The critical assumption are only anthocyanin gives out red colour during experiment and the content of anthocyanin in the every beetroot disc is the same (Do you mean even distribution of the pigment in the beetroot? ). Procedure: 1. Label 10 test tubes as A,B,C,D,E,F,G,H,I,J. 2.
Cut 25 thin discs(2mm thick) of beetroot tissue vertically and rinse them in excess water for about 15 minutes to remove the red pigment from the damaged cells. (Do you need to obtain cylinders of tissue using a cork borer? 2mm is too thin since this will cause too much mechanical damage to the tissue during cutting) 3. Pour 5mL of the 4 brands of mouth rinse into A,B,C,D respectively and add 5 beetroot discs to the tubes separately. Pour 5 mL of the 4 brands of mouth rinse to E,F,G,H respectively but without adding the beetroot discs. Pour 5 mL of distilled water into I,J.
For tube I, add 5 beetroot discs to it while without adding the beetroot discs into the tube J. a tube E containing water is needed to serve as a control. F to I should contain water and discs from A to D should be taken out after 1 to 2 min. and placed into F to I respectively. 4. Blot the discs dry with tissue paper and put four discs into the tubes. Note the time immediately. After 1 to 2 min. , transfer discs to F to I as described above. 5. Swirl the tubes from time to time to facilitate diffusion. 6. At the end of twenty minutes, compare the colour intensity of the water in F to I by visual observations after removing all the discs. . By comparing the one without adding the beetroot discs for calibration, note the change in the colour intensity of the set-ups. (should be deleted) 8. Repeat the experiment with the above procedure. (why? you have plenty of time? ) Precautions: 1. Rinse the beetroot tissue in distilled water to remove the leaked red pigment, anthocyanin. 2. Ensure the thickness of the extracted beetroot tissue is the same and cut the tissues vertically to ensure same surface area. 3. The first and the last cut beetroot tissue should not be used because the epidermis of the tissue is impermeable to the solvent which affects the diffusion rate. Why not peel the skin off beforehand? ) 4. Vigorous shaking of the solvent should be avoided to prevent the splint of the solvent. Swirl the tubes gently to ensure even concentrations of the solvents instead. 5. Blot the beetroot discs dry to avoid the change in volume of the solvent. If forceps is used, make sure it does not punch and destroy the beetroot tissue. 6. Use a white tile to better see the colour change. 7. Rinse the apparatus with distilled water and the solvent it is used to add when repeating the experiment.