It is expected that a point will be reached where the rate of reaction will remain constant because the number of hydrogen peroxide molecules will be greater than the number of active sites on the Catalase molecules. Beyond this point no matter how much more hydrogen peroxide s added the Catalase can’t increase the rate of the reaction. Therefore maximum velocity is reached as the rate of reaction is constant. The methods that will be used to determine the rate of reaction is: Rate of Reaction = Volume of Oxygen / Time of Reaction.
Preliminary Testing: The preliminary was carried out to decide on the number of measurements to be taken, in order to construct reliable, useful and accurate results. It was of extreme importance to do this in order to determine the different concentrations of hydrogen peroxide and Catalase. As well as to determine the time for each sample to be tested, to examine the apparatus, to observe and put right any errors within the method and to determine how all important variables are to be controlled to produce reliable results.
In addition to that, preliminary work was vital in assessing the terms of safety within the procedure by identifying any potential risks in substances, equipment, procedure and the disposal of materials safely. Hydrogen Peroxide, as explained above, decomposes to form oxygen and water. The apparatus was set up so that it would measure the volume of oxygen released in a given time so that the rate of reaction at that time, for each tissue, at each concentration could be calculated. This method was found to be more accurate and reliable to that of counting the number of bubbles released at a given time.
This is because counting the number of bubbles produced accurately in a Catalase experiment would be impossible as a lot of oxygen is released at the same time. The different concentrations of hydrogen peroxide were made up using a 10vol concentration to begin with and diluting it with distilled water accordingly (as shown in step 7 of the ‘method’). These concentrations were created to a suitable range in order to convey a difference in the affect on Catalase, if any, between them. Six different concentrations were chosen rather than a smaller amount to ensure this.
However, if a greater number of concentrations were chosen timing difficulties would be faced. Each time a concentration of hydrogen peroxide was placed in the conical flask the Catalase solution was poured over it. A rubber bung was immediately placed over the conical flask and the stop clock started. Each reaction was timed for five minutes and the volume of oxygen produced recorded at sixty second intervals. This procedure was repeated at each hydrogen peroxide concentrations. The concentrations that will be tested are: 1. 0M (10ml Hydrogen peroxide)
0. 8M (8ml Hydrogen peroxide/2ml Distilled water) 0. 6M (6ml Hydrogen peroxide/4ml Distilled water) 0. 4M (4ml Hydrogen peroxide/6ml Distilled water) 0. 2M (2ml Hydrogen peroxide/8ml Distilled water) 0. 0M (0ml Hydrogen peroxide/10ml Distilled water) Equipment list: Hydrogen Peroxide (10 Vol) Catalase (100%) Delivery Tube Burette Clamp and stand Distilled Water Timer Water Bath Beakers Thermometer 25ml Conical Flask Pipette Goggles Lab Coat Gloves Diagram: Method: 1) Switch on the bath at 30i?? C (confirm Temperature with Mercury thermometer).
2) Set up the Equipment as show in the diagram above. 3) Create Catalase solution by adding 0. 32ml of Catalase to 1. 68ml of distilled water in a 10ml beaker. (Use 1ml pipettes to measure these values. Note: Use and label two different pipettes for each solution). 4) Create Hydrogen Peroxide solution as shown above in concentration section. (Note: use 10ml pipettes, separate pipettes for each solution). Pour the hydrogen peroxide solution into the 25ml conical flask. 5) Pour the Catalase into the flask and place the stopper on the top, and start the timer.
6) Record Results for every 60s Results: H2O2 (ml) H2O (ml) Catalase (ml) Vol. of Oxygen (ml) Time (s) The problem encountered in this preliminary test was the high concentration on Catalase. It should now be changed to a lower concentration for a re-test. Unfortunately the reactions were so fast that a lot of the oxygen was released before the bung could be placed on the conical flask. In this re-test the 7) Create Catalase solution by adding 0. 2ml of Catalase to 2.
5ml of distilled water in a 10ml beaker. (Use 1ml pipettes to measure these values. Note: Use and label two different pipettes for each solution). H2O2 Conc. (mol) Volume of Oxygen Produced (ml) in the given time s can be seen by the results, the volume of oxygen released, by the action of the Catalase on the hydrogen peroxide decreased with lower substrate concentrations, indicating a decrease in the rate of reaction, as expected.
This is because at low hydrogen peroxide concentrations there are fewer substrate molecules to bind with the larger amount of Catalase molecules to form substrate-enzyme complexes, and therefore lowers the rate of reaction. Risk Assessment: Risk: H2O2 (Hydrogen Peroxide) Problem: It is an extremely powerful oxidising agent that’s toxic and harmful to clothes and any body parts e. g. skin, eyes. Precaution: Goggles, lab coats and gloves will be worn to minimise and injuries that may occur throughout the practical. The H2O2 will be stored in a labelled laboratory container with a lid on at all times when not in use.
Labels are also put on all beakers. Implementation: The experiment was carried out in order to test the hypothesis stated before. The procedure used on the day of the experiment is explained below: Hydrogen peroxide and distilled water was poured into each of the beakers, which were labelled appropriately with their contents. The amounts needed for each concentration were measured using separate pipette for each substance. With the distilled water, slightly more than 10ml was drawn up, and then the excess pushed out of the pipette into the sink, to the required volume.
Instead of making up the two sets of the six hydrogen peroxide concentrations from the beginning of the experiment as planned, one set was made up at a time. This was to avoid leaving the hydrogen peroxide exposed to air for long periods as it could decompose and therefore would create an inaccuracy in the results. The test tubes were labelled appropriately with the hydrogen peroxide concentration in vols. This was to prevent mistakes from happening as well as to ensure the correct concentration was used each time during the experiment. The apparatus was setup as shown in the planned method.