I hope to find the temperature at which the enzyme performs best and the temperature at which the rate of reaction slows down showing the enzyme has become denatured.
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An enzyme is a biological catalyst which alters the rate of reaction without being changed itself. Enzymes are proteins;they have very precise three dimensional shape,which forms a one specific active site on the enzyme.Each enzyme can only convert one kind of substrate molecule in to one kind of product molecule.These are specific.
(enzyme and substrate diagram)
Hypothesis.
During preliminary work,I tried two different methods.These methods were:
- Counting the number of bubbles produced during a time limit of two minutes.
and
- Using an upside down measuring cylinder filled with water in a water bath an feeding a rubber tube up into the cylinder and seeing how much of the water had been pushed out in a set amount of time.
I decided to use the bubble counting method because I have a set time limit of one hour in which to do my experiment.Also I thought that the bubble counting method is simple and effective and might possibly be more accurate than the other method I tried.By counting bubbles, the rate of reaction is shown more clearly as the temperature is increased and decreased over a range of temperatures.
With the other method, it was very hard to see how much of the water in the measuring cylinder was pushed out by the gas that was made during the reaction.Also, it took alot longer to get a clear, result.
These are the results I gained during my preliminary work.
Temperature heated to. Amount of bubbles produced.
15 c 21
25 c 27
35 c 0 (drew up water)
45 c 0 (drew up water)
55 c 0 (drew up water)
I have decided to keep these results and compare them with the results I get when I do the actual experiment.
Method.
Collect the following apparatus:
- Bunsen burner.
- A boiling tube.
- A test tube.
- A beaker.
- Rubber tubing attached to a boiling tube stopper.
- A measuring cylinder.
- Safety goggles.
- Hydrogen peroxide.
- A piece of potato.
- A test tube holder.
- A stopwatch.
- A tripod.
- A wire gauze.
Put on your safety goggles.
Set up the apparatus as follows:
(apparatus once fully set up)
- Fill the beaker with about 200ml of water.
- Use the measuring cylinder to measure out 15cm3 of hydrogen peroxide and pour it into the boiling tube.
- Place thermometer into the boiling tube and place the boiling tube into the beaker and heat to the desired temperature.
- Fill the test tube with water but not too much as the some of the water may be taken up the rubber tubing.
- Cut the potato to 2cms long making sure all skin is removed.
Once you have heated the hydrogen peroxide to the temperature you want, place the boiling tube in a test tube holder making sure the rubber tubing can be inserted into the test tube containing water.
- Place the cut potato into the boiling tube and make sure the stopper is in place and the rubber tube is in the test tube containing the water.
- Start the stopwatch as soon as the stopper is in place.
- Time the experiment for 2 mins counting the number of bubbles that appear in the water.
- Record your results and empty the boiling tube.
-
Repeat the experiment five times each time increasing the temperature.
Results.
The five temperatures (degrees c) I heated the hydrogen peroxide to were:
- 10 c,
- 25 c,
- 35 c,
- 45 c and
- 55 c.
I will show my results on a table and a graph.
Temperature heated to. Amount of bubbles
10 c 12
25 c 17
35 c 21
45 c 9
55 c 0(drew up water)
(graph with line of best fit)
I did not do the experiment with the temperature of 15 c because when the temperature was taken at the end of each experiment, these are the temperatures that the hydrogen peroxide rose to:
Temperature heated to. End temperature.
10 c 17 c
25 c 27 c
35 c 37 c
45 c 48 c
55 c 58 c
- 55 c did not produce any bubbles, instead the rubber tubing drew up water.
Conclusion.
By increasing the temperature of the Hydrogen Peroxide the Catalase reacted faster as I predicted. This is because I have studied the rate of reactions in previous work. At 37 c the Catalase worked best because that is the temperature of the human body. The rate of reaction increased as the temperature increased but denatured after 37 c.The enzyme's rate of reaction decreased rapidly when the temperature passed 37 c because the enzyme no longer fit the substrate, therefore the enzyme had to work harder to create a reaction and it eventually becomes useless and stops working.
When I heat the enzyme, it works faster because the particles have more room to move, vibrate faster and are uder less pressure.
Evaluation.
I think the procedure used was very efficient and practical.The experiment went well and was not too time consuming.The results were as I predicted.The experiment worked as well as I wanted it to.The results were satisfactory and satisfied me.
In my opinion,the experiment could have produced more accurate results than the results that were obtained.Instead of heating the Hyrogen Peroxide to the desired temperature then putting the potato in,the hydrogen peroxide could have been timed for 1 minute after being boiled so that the temperature could settle down.This might have affected the results that were obtained.
Also,instead of using the bubble counting mehtod,a gas syringe could have been used to see how much oxygen was given off.This would have given a much more accurate result than the results obtained.
The potato had to be cut and then left in the open air until it was required.Instead of the potato being left in the open air,the potato could have been kept in an air tight container until it was required.By leaving the potato in the open air for too long,the oxygen in the air may have started to react with the potato,therefore affecting the performance of the catalase,in the potato,in the hydrogen peroxide.
By putting the hydrogen peroxide in a water bath,the hydrogen peroxide would have stayed at the same,constant temperature throughout the experiment.Unfortunatly,there were not enough water baths, so we had to heat up the hydrogen peroxide to the desired temperature and then carry on with the experiment which meant that the temperature of the hydrogen peroxide fluctuated during the experiment which more than likely affected the overall results.
Also,the hydrogen peroxide was measured in a plastic measuring cylinder which meant that the amount of hydrogen peroxide might not have benn the exact amount.If an electronic liquid measurer had been used,the amount of hydrogen peroxide would have been more accurate and also the results may have been more accurate.
The distance the rubber tubing went into the water in the test tube would be another issue regarding the accuracy of theexperiment.Each of the five times the expeiment was carried out,the rubber tubing was always a different distance in the test tube which means the further in the tubig was,the more water was taken up.This would affect the results because the more water taken up by the rubber tubing,the longer and the more oxygen it would take to push the water out.This means that if the experiment was done 3-5 times at the same temperature,the amount of bubbles would be likely to change.
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Out of the two methods used,this was probably the most reliable because it was clear and you could tell that gas was actualy being produced because the bubbles were very easy to see.
I think this experiment was a fair test because it was timed each time with an accurate stopwatch.I am very pleased with the results I obtained.
