As the temperature continues to increase, to above 40, the enzyme and the substrate molecules move even faster. However, the structure of the enzyme molecule vibrates so energetically that some of the bonds holding the structure together begin to break. The enzymes begin to lose its globular shape, which affects the active site so much so that the substrate will no longer fit in it. The enzyme is said to become denatured and will not regain its correct shape even if the temperature is lowered.
Aim: In this investigation, the intension is to discover the influence of pH on the activity of potato catalase.
Safety: Wear the correct safety equipment, including- safety goggles for eye protection. Lab coat and protect gloves for Protection against chemicals, in particular Hydrogen peroxide which is a corrosive. If chemicals spill onto skin wash off immediately.
Accuracy: In order to be as accurate as possible and therefore to get the most accurate results, all the chemicals will be measured out as equal as possible and the reactant, the potato will be cut evenly using a ruler displaying millimetres.
Equipment required:
Razor blade x 1
Cork borer x1
Petri dish x1
Boiling tube (with rubber bung) x1
Stand x 2
Clamps x 4
Manometer tube (approx 2mm in diameter) x1
Beaker x 1
Syringe (5cm3) x 2
Glass syringe x 1
Clip x1
Stop clock x1
Potato tube x1
Prediction: The amount of oxygen produced will be at its maximum at approximately pH 7.The reason for this is that the enzyme being used in this experiment, Catalase, prefers more neutral conditions and will therefore produce more oxygen during this experiment.
Method: 1) with a cork borer cut cylinders of potato tube tissue into about 1mm in diameter and 6 cm long. Place a ruler beside the cylinder. Cut the cylinder into discs 1mm thick. As the discs are cut, place them under water in a Petri dish; continue until you have approximately 60 discs.
2) After completing the above, assemble the apparatus, and then remove the rubber bung from the neck of the boiling tube. With a syringe, place into the boiling tube 5cm3 of buffer solution at pH 3.carfully add ten potato discs. Then, with another syringe, add 5cm3 of hydrogen peroxide into the boiling tube.
3) As soon as the hydrogen peroxide has been added, replace the bung, making sure it has an airtight seal.
4) As the reaction begins and oxygen is being produced the glass syringe should begin to fill up with the produced oxygen. Should be timing this experiment and measuring how much is produced every 20 seconds.
5) After this is completed, remove the bung and wash out the contents of the boiling tube and repeat the same experiment to reassure the accuracy and results.
6) Now carry out five further tests, each repeating twice with 10 new potato discs. Follow the same procedure as before but with buffer solutions of pH 4, 5,6,7,8 in turn making sure a clean syringe each time.
Diagram
Results: pH 3
pH 4
pH 5
pH 6
pH 7
pH 8
Averages:
Anomalies: As you can see there is a highlighted result which doesn’t follow the same pattern that all the rest of the results do. This is an anomaly. The cause of this is unknown but the following things could be the reason(s) –The potato discs may have been cut unevenly, the syringes used may have been contaminated by being used in a previous experiment e.g. with a different buffer or the bung may not have been replaced after the hydrogen peroxide has been added.
Evaluation: this experiment was very successful, excluding a small minority of anomalies. My prediction has been proven correct in the fact that the enzyme used, catalase, does indeed prefer more neutral conditions. The results follow a general pattern, the more acidic the solution is the less oxygen is going to be produced, and it is the same with high alkali solutions. To continue my investigation there is a lot of factors, which affect the rate of reaction, could that could change, for example the type of enzyme could change. An enzyme that prefers more acidic conditions could be used or the amount of time could be extended or diminished.