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Beetroot contains red pigments called betalains, located within the cell vacuole. Normally the pigments can't pass through membranes but they leak out when the beetroot is cooked.

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Introduction

Why Does The Colour Leak Out Of Cooked Beetroot? If you read a recipe for cooked beetroot it will usually recommend that you don't remove the outer skin of the beetroot and don't cut off al the stalk and root if you want to avoid getting lots of red dye in the cooking water. Beetroot contains red pigments called betalains, located within the cell vacuole. Normally the pigments can't pass through membranes but they leak out when the beetroot is cooked. Aim - The aim of this practical is to use beetroot to examine the effect of the temperature on cell membranes and relate the effects observed to membrane structure. To function correctly a cell needs to be able to control transport across the partially permeable cell membrane. Theory - To understand how the red pigment leaks out of the beetroot it is essential that we understand the molecular Structure of a plasma membrane. A membrane is a phospholipid bilayer. This means that it has two layers of molecules called phospholipids. Each of these phospholipid molecules has two parts: � A 'head' that will mix with water but not with fat (i.e. it is hydrophilic) � Two 'tails' that will mix with fat but not with water (i.e. they are hydrophobic). In the phospholipid bilayer, the hydrophilic heads are always on the outside of the membrane. The hydrophobic tails are always on the inside of the membrane. Alone, this arrangement of phospholipids would form a barrier to water and to water-soluble substances. ...read more.

Middle

The pressure of time usually puts a limit on the number of replicates that can be taken. To be reliable, measurements should also be accurate. To be accurate a measurement should be close to the true value. Precision involves the choice of apparatus and the skill with which it is used. I had to also be aware of the different types of error that could occur in my experiment, systematic (values differing from the true value by the same amount) or random (values lying equally above or below an average value). I will make sure I no how to use all the apparatus correctly, because it is this problem that leads to a systematic error in the results, making them invalid. I will make sure I know how to calibrate the colorimeter before use. I will also make sure that I give my full concentration and attention towards the experiment, as it is a lack or wane in students concentration, which causes a random error to occur. The occurrence off a random error can be reduced if appropriate sensors or data loggers are used, it can introduce objectivity. Variables - The independent variable is the factor that is being varied. A rang of values for the independent variable can be chosen. The dependant variable depends on the value of the independent variable. The dependant variable is the one that is measured in some way. Any other variables that may affect the dependant variable should be controlled (kept constant) ...read more.

Conclusion

The hydrogen bonds between the proteins break due to the high temperature and so do the di-sulphide bonds. Referring to my hypothesis I predicted that denaturing would occur at 45 degrees Celsius. Thus I would not of expect a lot of change in the percentage transmission between 20 and 30 degrees Celsius. Because at 30 degrees Celsius I would have presumed that the membrane would have been fairly stable. However my graph shows the contrary. This might be due to sources of error in my experiment. Experiments - I have successfully gained my results that back my hypothesis. However the results have limitations and some sources of error. The size of the beetroot is essential. In my experiment I used a ruler and cork bore to measure out the same size beetroot. The cork borer was a a good aid as it ensured that the beetroot had the same diameter. However using a ruler could present possible error. Due to the surface area to volume ratio. As the test tubes were taken out of the water bath and placed the in the colorimeter the temp reduced by a few degrees. This small error could of change the results by 0.5 percent inaccuracy. This is because of insufficient equipment. I understand this experiment is only on a small scale but to gain better results each test tube going up in 10 degrees Celsius so we can tell the point of denaturing more accurately, however I feel that I my experiment showed breath of how a membrane functions under temperature change ?? ?? ?? ?? Hammad Naveed Biology ...read more.

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Marked by teacher Luke Smithen 17/09/2013

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