The concentrations that I will be using are:
- 10%
- 20%
- 30%
- 40%
I am going to be using a 10ml sample of H2O2 soln in each experiment
∴ 1ml of hydrogen peroxide soln = 10% concn
9ml = 90% concn
APPARATUS:
-
2 Boiling tubes, 10ml Measuring cylinder, 2x100cm3 Beaker, Delivery tube, test tube rack, syringe, bottle of distilled water, sieve, 50cm3 beaker, stopwatch.
To make my results reliable, repeat experiment will be done in all 4 concentrations and 3 times each.
20 beads of immobilised catalase will be used in each experiment to maintain and equal surface area.
Production of Immobilised Enzyme:
What is needed:
-
2ml of Sodium Alginate Soln
- 2ml of Liver extract containing the Catalase enzyme.
-
50ml of calcium Chloride Soln
- Mix the Sodium Alginate and Liver extract together and make sure they are properly mixed.
- Draw mixture into a syringe and into the beaker of calcium chloride; make drops of preferably equal size into the beaker.
- As the drops enter the calcium chloride they will harden into small rounded balls.
- When you have used up all of the mixture, with a sieve collect the beads and rinse them off with a little distilled water.
METHOD:
-
Set up apparatus shown below:
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To make the desired concentration of hydrogen peroxide, get a 10ml measuring cylinder and for 10% place 1ml of hydrogen peroxide in with 9ml of distilled water. (CARE: Hydrogen peroxide is an irritant, keep away from eyes and clothes, as bleaching can occur.)
- Then place 20 beads into the boiling tube of Hydrogen Peroxide and insert the bung of the delivery tube back in and start the timer.
- Over a period of 2 mins. Count the number of bubbles produced from the reaction.
- After, repeat the experiment with 20% and 30% concentrations.
- When gaining the results for all three concentrations, do three repeats per concentration to gain reliable results.
RESULTS:
This graph shows the relationship that is present between the results. As the concentration of Hydrogen Peroxide is increased (coloured bars) the amount of Oxygen increases also. The concentration that was most effective on oxygen production was 40% (dark purple), with roughly around 140 bubbles produced in 2 minutes.
EVALUATION OF RESULTS:
There is a clear pattern in the results that show and increase in the production of O2. This is because the substrate number was increased; therefore more substrate-enzyme complexes were formed.
As I had some extra time and beads I decided to see whether the pattern changed at 40% concentration. I saw that the pattern continued the same path. This can be explained by looking at the solution more closely.
If the concentration of the substrate is increased then there will be more substrate molecules in an area. This will cause more collisions between them and the catalase and therefore more complexes and by-products (such as Oxygen is produced.)
= Enzyme
= Substrate
So if there were an increase in substrate numbers then the production of oxygen would be more significant.
We carried out the experiment in a controlled water bath because temperature would have a major effect on the rate of reaction. This is because the heat energy would be transferred to the molecules and would become kinetic energy, causing more collisions and leading to more complexes forming. Another factor is that the active site of the catalase may become denatured. Because all enzymes are proteins, they are consisted of amino acids, and when these long chains fold up the form an active site, which then can react with substrates. If too much heat energy is added, the molecule is vibrating with such energy that weak Hydrogen bonds that hold the tertiary structure of the protein together are broken. These results in reshaping of the active site, that is very specific to certain substrates, and therefore becomes denatured.
Although increasing the concentration of the substrate increases the rate of decomposition, if the concentration is increased too much the active sites on the enzymes will be saturated (occupied by substrates), this would then decline the rate at which Oxygen was produced.
I think the results that I gained show a clear trend forming from reliable results. If I were to repeat this experiment again I would like to prove whether what I can tell with my own scientific knowledge, that if I carried on increasing the concentration of Hydrogen Peroxide to a point where there were more substrates than enzymes, I would see a gradual decline in the amount of oxygen produced.
If I carried out such an experiment I would expect to see the pattern on the graph to look like this: