Syringe
(Contain catalase)
Bung
Clamp & boss
Conical flask
(Contain hydrogen peroxide)
Stand
The apparatus for this experiment
Risk Assessment
1.Hydrogen peroxide is a dangerous substance. It can cause serious injury to the eyes and skin. It is therefore necessary that goggles be used for eye protection. In addition, eye irrigation equipment should be readily available in case of an emergency.
2. The working area must be clean, tidy and dry. Make sure there is no obstacle in the working area so that you can easily move around as. This allows you to perform the experiment safely and unimpeded care should be taken to ensure that liquid is not spilled onto the floor to cause slippage.
Result tables
The table of results is shown below (table 1). It shows the volume of oxygen gas produced when hydrogen peroxide reacts with celery extract in 30 seconds, 60 seconds, 90 seconds and 120 seconds at the temperature of 15°C, 25°C, 35°C, 45°C and 55°C.
Table 1.
Table 2 (below) displays the results from the repeated experiment.
Table 2.
Table 3 (below) shows the results obtained when the experiment was conducted for the tired time.
Table 3.
Average:
Table 4 shows the average taken from the results of the above three experiment
Table 4.
The following calculations shows the volume oxygen gas produced per second for each temperature for the first 30 seconds of the experiment. The first 30 seconds were chosen for this because the volume of oxygen produced during this time can be measured most accurately.
15°C:
9.33ml / 30sec = 0.31ml/sec-1
25°C:
11.83ml / 30sec =0.39ml/sec-1
35°C:
14.17ml / 30sec = 0.47ml/sec-1
45°C:
16.67ml / 30sec = 0.57ml/sec-1
55°C:
7.33ml / 30sec = 0.24ml/sec-1
Conclusion
The enzyme molecules have active sites that help them to recognize their substrates in a very specific way. Just like a key only fits into a specific lock, each enzyme has its own specific lock, each enzyme has its own specific substrate. This is called the lock and key theory. The enzymes never actually get consumed in the process; they just increase the rate of reactions.
Temperature influences the rate of enzyme activity. The temperature at which the enzyme was most reactive and at which the greatest volume of oxygen was produced is called the optimum temperature. The breakdown of Hydrogen Peroxide accelerates as the temperature increases until the optimum temperature after which it begins to slow down. Usually a 10°C rise in temperature causes a large increase in the rate of the enzyme activity. This is only true up to an optimum temperature. Beyond this point, the 3D shape of the active site becomes distorted and the enzyme becomes denatured and therefore inactive.
This experiment proved the optimum temperature is 45°C. At 15°C, 25°C and 35°C, the volume of oxygen produced was less than at 45°C, because the optimum temperature had not been reached. An increase the temperature causes the molecules to move faster and collide more often, therefore the speed of reaction increases, because the optimum temperature for the active sites to be engaged increased with the activity of the molecules.
From 15°C to 45°C the rate of the enzyme activity was rising. It was after 45°c that we could see a decrease in the enzyme activity. A rise in temperature increases the rate of most chemical reactions and a fall in temperature will slow them down because enzymes are proteins if the temperature exceeds 45°C the enzyme will be denatured and will no longer work at all.
Evaluation
The most important steps were adding enzyme solution into the conical flask and measuring the volume of oxygen gas produced. They are very easy to cause errors, on one accession, the apparatus was not checked before the experiment started, and as a result a leak occurred. So make sure that the apparatus is securely assembled, because the pressure of gas generated may cause the joints may leak if otherwise. After adding the catalase to the hydrogen peroxide solution (in the conical flask), the 3-way tap should be turned off immediately, so that no oxygen can escaped form the conical flask to the syringe. (The one we use to add catalase)
Another important factor could cause error is the temperature of the solutions, because the thermometers gives +/- 0.5°C of error.
The following measuring was identified as being important for ensuring accuracy whilst carrying out the experiment as well.
1.When hydrogen peroxide is measured in the measuring cylinder, care must be taken to make sure that the reading is taken from the base of the meniscus, because only by this means will read be accurate.
2.Care should be taken to ensure that the plunger of the syringe that is used to deliver the catalase is fully depressed so that the full volume of enzyme is added to the hydrogen peroxide.
Bibliography
Cambridge Advanced Sciences Biology 1, Mary Jones, Richard Fosbery, Dennis Taylor, Page 45-47
