To investigate the effect of temperature on catalase.

How temperature effects the breakdown of hydrogen peroxide by the enzyme catalase

Aim: To investigate the effect of temperature on catalase

An enzyme is a protein molecule that speeds up chemical reactions in all living things, without enzymes these reactions would be to slow or would not happen. Enzymes are also useful because they cannot be used up and does not affect the reaction in any other way. My experiment will be testing the affect of temperature on catalase. I will need to try and keep these constant for the experiment to be fair:

1. PH: if the pH is too high or too low the enzymes will become denatured because of the loss of H+ ions at too high PH, and the gain of H+ ions when the pH is low.

2. Concentration of enzyme: The higher the concentration, the more successful collisions occur and the higher the rate of reaction. I will try to keep the same concentration of enzymes by using the same volume of potato.

c) Surface area: If the surface area is larger there will be more successful collisions. I will try and keep this constant by measuring and cutting accurately.

Kinetic theory states that when a substance is heated, energy is given to the particles and they vibrate faster. Therefore when heat is applied to an enzyme and substrate, the particles speed up, increasing the rate of successful collisions with each other. This would suggest that the rate of reaction should increase as the temperature is increased. But this is not completely true because if the temperature is too high the enzymes become denatured and stop working. Enzymes become denatured at high temperatures and change shape because they have a protein coating and will not be able to work again. Now the substrate will not be able to fit into the enzyme like the key and lock theory, and the substrate will not be broken down. Enzymes need an optimum temperature, so if the temperature is too low the enzyme will become dormant.

Prediction

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Prediction

I predict that there will be the highest amount of successful collisions at 40 C because that is body temperature and amylase is found in the body that is roughly 37 C. I think anything above will cause the enzymes to denature because the heat will change the shape of the protein molecules. The break down of starch will increase up to 40 C, because the increase in temperature will supply the enzymes with more energy to react, and then it will drop because of the enzymes being denatured. I predict that any temperature above 40 C will cause the enzymes to denature because every enzyme has a range of optimum activity. The high temperature will supply enough energy to break some of the molecular bonds. The active site now becomes altered in its ability to accommodate the substrate molecules it was intended to catalase. From other knowledge it is true the as temperature increases, the rate of reaction also increases. But the stability of the protein also decreases due to high temperature.

I will keep these constant to ensure it is a fair test:

Same volume of hydrogen peroxide solution

Same pH

Same concentration of potato

Constant temperature

I will make this the variable:

Temperature

Apparatus

5 water baths

3 test tubes

Test tube rack

3 Thermometers

2 potatoes

Scalpel

Stopwatch

Ruler

Certain amounts of hydrogen peroxide

Measuring beaker

Diagram

Method

Set up the 5 water baths at o C, 40 C, 60 C, 70 C, 80 C

I will also be doing this experiment at room temperature but does not need a water bath

Set up apparatus like diagram above

Cut the potato so you will get 3 small pieces with the dimensions 5cm by 1cm by 1cm.

Add 30cm of Hydrogen peroxide to each of the 3 test tubes by using the beaker.

Put three thermometers in each test tube

Put the three test tubes in the rack and put the rack in the 0 C water bath.

Wait until the temperature reaches the temperature of the water bath

Add one of the potato slices into one of the three test tubes and start your stopwatch

After 2 minutes record the height of bubbles cm for that test tube and record the results.

Rinse the solutions in the sink and put the potato in the bin

Repeat this experiment two more times with the two other potato slices and take an average

Repeat experiment with different potato slices in the other water baths at different temperatures and do the room temperature one by using the rack on the table.

In order to observe the effect of temperature on catalase i will be maintaining the amount of oxygen released. The oxygen produces a froth, which I will measure in cm

I calculated the average by adding the three results of the height of bubbles at that temperature and then dividing it by three.

Results

Conclusion

My results according to the table and graph indicate that the optimum temperature for the enzymes is 60 C. This is the opposite of my prediction, which was that the optimum temperature would be 40 C, and any temperature higher than that will cause the enzymes to denature and the rate of reaction would depreciate. The main reasons being why my evidence did not turn out as expected was because:

1.I did not wait until the temperature of the hydrogen peroxide reached the temperature of the water bath.

2.The potato was not cut accurately

Because I did not wait until the temperature of the hydrogen peroxide reached the desired temperature, the results were altered because the temperature was always rising hence the higher temperatures reached the optimum temperature of the enzyme while the water bath at 40 C did not reach the optimum temperature or only reached there at the end and was not there long enough. The potato was also not cut accurately so the surface area was different, the mass was different and the amount of catalase was different. This affected the experiment because if the surface area is larger there will be more collisions and if smaller there will be less collisions. If there was more or less enzymes the rate of reaction will be higher or lower because there are less enzymes to do their jobs.

Evaluation

There were a lot of errors in my experiment in both how the experiment was conducted and the results.

My method that gave the evidence was not reliable at all and it was completely my fault. The main reason why my experiment was not successful was because I did not wait until the temperature of the hydrogen peroxide reached the desired temperature, the results were altered because the temperature was always raising hence the higher temperatures reached the optimum temperature of the enzymes. The results were not fair at all because of the above reason. I do not have enough evidence to draw a conclusion due to the fact that my results are not reliable or precise. The other reasons why my experiment did not go right were because the potato was not cut accurately, so the surface area or the amount catalase was not always the same. I thought that the pH would remain constant but it could of varied.

If I were to do this experiment again I would:

1.Wait until the hydrogen peroxide reached the desired temperature and then put the potato in. This would make the test much more fairer as when the potato was in the hydrogen peroxide the temperature would remain the same. It would also be fairer because the temperature was supposed to be kept constant and instead was a variable.

2. I would turn the potato into paste and measure the volume. This way the amount of enzymes would be similar in each test. Or I would use a template to cut the potato, as this would give more accurate cutting.

If I had just done number 1., the whole test would have been fairer and due to that, my evidence cannot support my conclusion.