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An investigation to find out how temperature affects membrane permeability.

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Introduction

An investigation to find out how temperature affects membrane permeability. This Problem What we will hopefully try and find out in this investigation is if temperature affects the permeability of a beetroot membrane Hypothesis As the temperature in which the beetroot is put in increases there will be more red dye diffusing out of the beetroot due to the denaturing of the proteins in the cell membrane as a result of the high temperatures. Background Knowledge The cell membrane can be represented as the fluid mosaic model as shown below. It is selectively permeable and controls what enters and exits the cell. It does this by proteins, however small lipid molecules, non-polar molecules and small water molecules can enter and exit the cell straight across the membrane through the phospholipids, due to the properties of the molecules enabling them to do so. Extrinsic and intrinsic proteins in the cell membrane help other the molecules enter or leave the cell by either facilitated diffusion or active diffusion. Different proteins are specific to certain molecules hence the cell membrane being selectively permeable. Here is a diagram of the cell membrane: As you can see the cell membrane is made up of a phospholipid bilayer which the extrinsic and intrinsic proteins span through. Some of the extrinsic proteins act as antigens for cell recognition with a carbohydrate attaching to then forming a glycoprotein. ...read more.

Middle

used to place the solution of the three red pigments in Pipettes Are used to put the red pigment from each boiling tube into each cuvette: Colorimeter This is a piece of digital equipment that measures optical density (light absorbency) in Arbitrary units. This is what tells how much red pigment has been lost by the beetroot This coursework from www.coursework.info Test tube racki Used to put the boiling tubes in when using the colourimeter Diagram of equipment Plan The variable that will be changed in this experiment will be the temperature of each water bath. The steps of each measurement will be 30, 40, 50, 60, 70, 80, 90 and 100 degrees centigrade. I have chosen these steps because I have predicted that 40 �C will be the optimum temperature for the beetroot and will indicate little red pigment diffusing out of the beetroot therefore showing if the cell membrane has kept its integrity. Referring to my prediction 30 C should show the temperature being to low for the proteins to work properly, and as a result show little permeability in the cell membrane. The other temperatures beyond 40�C will show the beetroot being denatured, with more red pigment as the temperature increases, diffusing into the distilled water. I will change the temperature by heating up the glass beaker, which contains water acting as the water bath and the 3 boiling tubes containing distilled water, to the desired temperature using a Bunsen burner. ...read more.

Conclusion

When cutting up the pieces of beetroot in the first place the membrane of part of the beetroot will be broken resulting is red pigment being lost. This acts as excess pigment, which we do not want to measure and therefore we would need to get rid of it. The best way of doing this is the rinse each piece of beetroot that you have cut under distilled water, this will get rid of that excess pigment and therefore you will only measure the red pigment that has been lost in the boiling tubes. Keeping an eye on how long the beetroot is in the water bath for is also important, as already stated earlier in the plan. Making sure that you don't get any finger marks on the cuvettes when using the colourimeter is also important because if any marks get on the clear sides of the cuvettes the cuvettes will be darker and therefore more light will be absorbed. Also making sure that you read the reading of the thermometer at eye level will make sure that you record the reading correctly. I will do 3 replicates for each measurement i.e. there will be three boiling tubes in a specific water bath. Doing this will enable me to take and average of all replicates and therefore discounting any anomalous results. Abid Zaman ...read more.

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