Apparatus
5 test tubes, 5 Boiling tubes, 1000cm ³ beaker, 25cm ³ measuring cylinder, water, 10cm³ measuring cylinder, delivery tube with bung, Hydrogen Peroxide, Catalase, stop-watch, test tube rack, syringes, water bath, thermometer
Analysis
The graph obtained for 100% enzyme concentration starts off steep and then slows down, this is because at the start of the reaction, there is more substrate available to bind with the enzyme’s active site, therefore the reaction between the catalase and Hydrogen Peroxide is a lot faster and more oxygen is being produced. By the end of the three minutes the reaction will slow down because there is less substrate molecules available for the enzymes, so the enzymes just go around searching for a substrate to fit into their active site, this means less collisions and less oxygen being produced.
These results apply for the concentrations of 80% 40% and 20%. However in the class results, enzyme concentration of 100% has a higher amount of oxygen being released followed by 80% 40% and 20%.
This shows that the higher the enzyme concentration is, the faster the rate of reaction will be and that there will be a higher amount of oxygen released.
The more enzyme concentration there is the more active sites available for the substrate to slot into. Therefore as long as there is plenty of substrate available the rate of reaction will increase linearly with enzyme concentration. The amount of volume of oxygen released and collected will always be higher at the beginning of the experiment and then will gradually slow down and eventually stop. This is because when the enzyme and substrate are first mixed, the amount of substrate is at its highest and wont be hard for enzymes to find a substrate to bind with its active site, but as time goes on its harder for an enzyme to find a substrate to bind with so the reaction slows down.
Evaluation
The suitability of the experiment was very good as it provided me with the required information and also the experiment was easy to carry out. This was because I only had to combine the hydrogen Peroxide and catalase together and place in the boiling tube with the bun on top. The oxygen that was released would travel up the delivery tube and up through the water filled measuring cylinder. This would force the water out of the cylinder, showing how much oxygen was being released every 30seconds. This allowed me to read off the amount released very efficiently.
The experiment was also easy to carry out because I knew an exact time to take the readings and when to stop the experiment, also you could tell that the experiment was going right because the oxygen was showing at the top of the measuring cylinder, this showed that the reaction between the Hydrogen Peroxide and catalase was taking place.
However there were a few anomalous results within my experiment, which shows up on my graphs.
The only experiment that went as predicted was the 80% enzyme concentration of which showed the trend of the graph starting off steep because of the high amount of substrate molecules available to bind with the enzyme’s active site and then gradually slowing down.
The 100% concentration had a lower amount of oxygen released compared to the 80% enzyme concentration. This surprised me because the higher the enzyme concentration is the faster the reaction takes place and the higher the amount of oxygen released is greater. This may have been due to Hydrogen Peroxide being present in the syringe whilst I used it to extract the catalase to place in the boiling tube. This would cause the reaction to start whilst in the syringe resulting in oxygen being released and lost. Also the bun might not have been placed on top of the boiling tube properly, so while the reaction was taking place the oxygen that was being produced only some of the oxygen was traveling through the delivery tube whilst the rest of the oxygen was being lost by escaping via the sides.
The 40% and 20% enzyme concentration also showed anomalous results because instead of the graph starting off steep and then gradually slowing down and going off to a curve, they both remained at a constant gradient. This didn’t show the trend of having a greater amount of oxygen being released at the beginning of the experiment than compared to nearer the end of the experiment.
There were some errors in the apparatuses I used because the bun that had to be placed on top of the boiling tube had to be placed securely on; this was so that no oxygen escaped from the sides which would make the experiment unfair and also inefficient. I could have used a gas syringe instead of the bun and delivery tube to calculate the amount of oxygen released as it may have turned out to be more efficient and easier.
The measuring cylinder I used was 25cm³ which was acceptable for enzyme concentration of 80% and 100% because the amount of volume that was being produced was more than the amount of oxygen being produced for enzyme concentration of 40% and 20%. Therefore I could read the measurements off quite easy, but for enzyme concentration of 40% and 20% less oxygen was being released so I should of used a 10cm³ measuring cylinder as the readings would have been more accurate.
The glass syringes I used weren’t accurate because as you extracted the Hydrogen Peroxide or the catalase from their beakers to the boiling tube the solutions would leak out from the sides resulting in less of the solution being used than required. This was inefficient because it meant there was either less substrate or enzyme concentration for the reaction and also the reaction would have been a lot slower than expected. I could of used pipettes instead of syringes as they would have been a lot easier to use and more efficient.
As instructed I should have repeated each experiment 3 times so that if they were slightly inconsistent, when I worked out the averages they would have been more precise and would have followed the trend of the class results, this was however because I didn’t have enough time to repeat the experiments for them to be more accurate. The class results followed the trend because averages were worked out from everyone’s results and then placed on a graph, so any anomalous results wouldn’t show up as much as they would of.
