Determine what effect with an increase in the surrounding temperature has on the plasma membrane of a beetroot cell structure.

An investigation into how the

the temperature affect the

permeability of cell

membrane

Aim:
This experiment aims to determine what effect with an increase in the surrounding temperature has on the plasma membrane of a beetroot cell structure.

Introduction:

The purpose of a cell membrane is to control the transport of substances moving into and out of a cell. The membrane is an extremely thin layer (8 to 10 manometers (nm)) thick, which is partially permeable. It consists mostly of lipids and proteins. The lipids found in cell membranes are phospholipids because they have one molecule of glycerol chemically linked to two molecules of fatty acids and a phosphate group.

Despite there are many differences in appearance and function, all cells have a surrounding membrane (called the plasma membrane) enclosing a water-rich substance called the cytoplasm. All cells have a variety of chemical reactions that enable them to grow, produce energy, and eliminate waste. Together these reactions are termed metabolism .

In the cells of a beetroot plant, a substance called anthocyanin is contained within the cell, inside the plasma membrane. It is anthocyanin, which gives the beetroot its characteristic blue/purple colour. If a cell is damaged in a beetroot plant and the membrane is broken, the anthocyanin 'bleeds' from the cells like a dye. It is this characteristic that can be exploited to test which conditions affect the integrity of the cell membrane.

Because I am experimenting with the effects of temperature on the membrane, i will place the samples of beetroot into a water baths of varying temperatures and measure the colour change in the water. Temperature is just one of the possible variables. Others include effects of poisonous substances such as alcohol and/or various solvents. The dependant variable (DV) in this experiment is colour change in water caused by anthocyanin leakage.

Temperature affects the permeability of cell membrane. As the temperature increases, the kinetic energy of molecules in the cell membrane increase, the collision frequency also increases, so the fluidity of cell membrane increases phospholipids spread out therefore more space in between them. Therefore more pigment inside the cell will leak out. As temperature increase there is more space for red pigment to pass through the phospholipid bilayer.

The increase in temperature can cause the bond holding the tertiary or quaternary shape break, the protein become denatured. And because when the temperature increases there is an increase in the kinetic energy of the protein molecules. The protein can then vibrate more violently, which disrupting the week hydrogen bonds and ionic bonds. The shape of the protein changes temporarily or permanently. And it no longer performs its biological function.

At lower temperature, the red pigment can still passed out by diffusion. They pass through the channel protein. The protein is a polymer of amino acid. Different protein have different properties are because of the amino acids. Amino acid generally has amine group and carboxylic acid group. The only way which amino differs from each others is due to the R group bonded in the central carbon. The R group has 4 properties:

1) Acidic - if they have COOH, they ionised easily releasing hydrogen ions.

2) Basic – NH2 group take up hydrogen ions from the solution.

3) Hydrophilic- they are polar e.g. amino acid with OH group

4) Hydrophobic-they are non polar amino acid with CH2 and CH3.

These properties help the influence the shape and therefore the function of any protein they make up.

Model of a Cell Membrane

Output variable:

*these are controlled so they all keep constant

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2) Basic – NH2 group take up hydrogen ions from the solution.

3) Hydrophilic- they are polar e.g. amino acid with OH group

4) Hydrophobic-they are non polar amino acid with CH2 and CH3.

These properties help the influence the shape and therefore the function of any protein they make up.

Model of a Cell Membrane

Output variable:

*these are controlled so they all keep constant

Hypothesis:
An increase in temperature will damage and denature the plasma membrane and cause the cytoplasm and other substances contained within the cell membrane to leak out

Materials:

Stopwatch: it is used to make sure the time taken is constant for the reaction.

Test tube: it is to provide a place for the reaction. And so the contact surface area is contact for the experiment.

Beetroot corner: this is to take cylinders of beetroots out of the whole beetroot and it has a radius of 1 cm which make it easy to work out the surface area of the pieces of beetroot.

A knife: this will be used to cut the beetroot cores into the length for the investigation.

Beetroot: this is the source for the investigation.

Distillated water: this is used to provide a place for the reaction.

Tissue paper: it is to dry up the beetroot.

Needle: it is used to held the beetroot in place so as to increase the surface area.

Thermometer: it is used to measure the temperature of the surrounds under the investigation.

Colorimeter: it is used to measure the transparency of the solution.

Water bath: it is used to provide different temperature for the investigations.

Test tube rack: it is used to hold the hot test tube.

Methods:
1) Before the experiment can start, the beetroot with the same size must first be prepared. To do this, we need the white tile, knife, glass rod and the corers.

2) The same diameter corers are made by pushing the corer into the beetroot and then withdraw it. The cylinder will remain inside the corer, so it must be pushed out with a glass rod. The entire beetroot piece must have the same surface area so as to have fair test.

3) Once a few good, uniform cylinders have been collected, they must then be cut into 15 pieces of equal length. The beetroot was cut to 2cm.

4) Because the beetroot has been cut some of the cell membranes had been broken, which means some anthocyanin will leak out. This must be completely washed off in order to maintain the reliability of the results.

5) Place a test tube into the beaker with hot water in it and put it into the water bath where the water bath must have been heated to 85¢XC (the maximum temperature for our experiment) I can measure the temperature by using the thermometer.

6) Once the water bath is at the correct temperature (measured using our thermometer), three pieces of beetroot held separately in the needle is then placed into the hot water directly and left for exactly 20 minute.

7) When the time is up, the beetroot pieces will then be removed.

8) The solution is then pour into the colorimeter test tube to do the measurement.

9) Steps 5,6,7,8 will be repeated with the other pieces of beetroot with the only difference being the temperature of the water. The temperatures will be using are 85°C, 70°C, 65°C, 60°C, 55°C, 42°C and 36°C.

10) Each time the pieces of beetroot are removed from the heated water, it will be left in the distilled water for exactly 30 minutes, before being discarded. The fluid in each of the test tubes will be analysed using a colorimeter and compared against the control, which is distilled water to check for any variations in the colour of the water.

N.B: a) shake the test tube frequently to reduce the error caused my osmosis.

b) Hold the colorimeter bottle with the rough side, do not tough with the

Smooth sides.

c) wash the beetroot and dry up with tissue to ensure the red pigment leak

Out is due to osmosis under the investigation.

Safety:

Use the knife, cork borer carefully and be care with the hot water bath. Uses the test tube rack when pick up the test tube from the water bath. Tight up with the long hair when carry out the experiment.

Fair test:

It is very important that I keep the other input variable the same because if they change then they can affect my investigation without me knowing it, which will be an unfair test. So this is how I will keep the other input variable the same.

I will keep the surface area constant. Which the beetroot should have the same diameter and the same length. I will keep the different pieces of beetroot come from the same one throughout the investigation. I will also have to keep the same solvent, which is distilled water. The only variable I will do is the temperature.

Results:

Conclusions:
After collecting and correlating the results, I have come to the conclusion that the experimental hypothesis is correct in that an increase in temperature will damage and denature the plasma membrane and cause the cytoplasm and other substances contained within the membrane to leak out. This has been shown by a steady increase in anthocyanin leaked out of membrane cells as the temperature increases.

The results increased fairly steadily with one exception at 65¢XC where the amount of anthocyanin actually reduces. This is almost certainly due to experimental error. It is the breakdown of the lipids which make up the plasma membrane that causes 'holes' to appear in the membrane, allowing fluids to pass out freely, but when the temperatures begin to get higher still, the proteins in the cells begin to decompose as well which blocks some of the holes and therefore slowing down the release of anthocyanin. It is these findings which explain why cells cannot maintain life in extreme temperatures.

Evaluation:
The results that were collected follow the same pattern as results collected by similar studies carried out within our class, so therefore it is safe to say that the results can be repeated reliably and the methods can be used universally.

It would have been beneficial to have repeated the experiment more times to make certain that the results were not gained through chance or by an external factor. The control experiment used was highly accurate, using distilled water, which is the clearest possible liquid, meant that even the slightest deviation in colour could be detected by the colorimeter.

Controlling the variables in the experiment is not an easy task. The first major problem is the size of the beetroot piece. The pieces could be the same mass, but have a very different surface area to one another. This obviously alters the effect of the experiment. The other difficult variable to maintain was the temperature of the heated water. With only basic equipment, keeping the water at the correct temperature was made a complicated task. External variables were well controlled. If the experiment was to be repeated, the use of a proper controlled water bath may be a consideration, and also a template made for cutting the beetroot pieces.

Using a beetroot as the sample is not a good representation of the whole eykaryote group. Other cell membranes may have better or worse heat tolerance, some may not be affected at all, however, using a beetroot does give a good representation of the theories behind the plasma membrane and how it behaves.