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Investigate how enzyme concentration can affect the initial rate of reaction.

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Introduction

Experiment 1: Hypothesis - My hypothesis for this experiment is that the 1% trypsin solution will have a fastest initial rate of reaction rate. Aim - * To investigate how enzyme concentration can affect the initial rate of reaction. Apparatus - * Milk powder solution (pre-made) * Stopwatch * 4 boiling tubes * Pipette * Measuring cylinder * Distilled water * 1% trypsin solution (pre-made) * 0.5% trypsin solution (made by combining 5 cm3 of 1% solution and 5 cm3 of distilled water) * 0.25% trypsin solution (made by combining 5 cm3 of 0.5% solution and 5 cm3 of distilled water) * 4 cuvettes * Colorimeter (set to record % absorbency) * Rod Method - 1. Pour 2 cm3 of already made milk powder solution into a boiling tube. 2. Measure out 2 cm3 of 1% trypsin solution and pour it into the boiling tube containing the milk powder. Stir the solution. 3. Using a pipette, take out 1 cm3 of the trypsin and milk powder solution and place the mixture into a cuvette. Measure the colour absorbency of the cuvette and record the reading. Start the stopwatch before taking the colorimeter reading. 4. Record the colour absorbency of the mixture every minute until the reading turns to 100%. Remember to reset the colorimeter before each reading. 5. Repeat steps 1-5 using the 0.5% trypsin solution and 0.25% trypsin solution, tabulating the data afterwards. ...read more.

Middle

The 0.5% solution had only a 64% reading at 7 minutes, reaching 100% at around 9.5 minutes. Discussion - A higher concentration means a higher number of enzymes in a fixed volume, therefore having a higher number of reactions in a given time (more active sites). Theoretically, in the experiment, the 1% trypsin solution should have contained twice the amount of trypsin than the 0.5% solution. The higher number of active sites meant that the 1% trypsin solution should have happened at double the rate of the 0.5% solution, due to the fact that there was twice the amount of trypsin reacting with the milk powder in a given time. The mixture clears up (100%) because all of the milk powder reacts with the trypsin eventually. Experiment 2: Hypothesis - My hypothesis for this experiment is that the more potato slices placed in the hydrogen peroxide, the faster the rate of reaction between the catalase and hydrogen peroxide, hence the more gas produced in a given amount of time. Apparatus - * Stopclock * Gas syringe * Measuring cylinder * Hydrogen peroxide * Retort stand and clamp * Stopper * Potato * One potato * One size 4 cork borer * 5 conical flasks * Knife * Ruler * White Tile Fig. 1 Method - 1. Using the cork 4 borer, cut out 5 strips of potato. 2. ...read more.

Conclusion

Time (sec.) Gas released (cm3) 30 1 30 2 60 2 60 4 90 2.9 90 5.5 120 3.8 120 6.6 150 4.5 150 8 180 5.1 180 9 210 6 210 10 240 6.8 240 11.1 270 7.3 270 12.1 300 8 300 13.1 10 slices Time (sec.) Gas released (cm3) 30 2.5 60 5 90 7 120 9 150 11 180 12.5 210 14 240 15.2 270 16.7 300 18 Conclusion: From the table and graph, we can see that my hypothesis proved correct. The conical flask containing 10 slices released gas at a faster rate and also at a larger amount. From the graph, we can see that the lowest rate of reaction was the flask containing 2 slices. The order then went from 4, 6, 8, and then to 10 slices. My results were quite good because looking at the graph, the amount of gas produced every 30 seconds in the conical flask containing 4 slices of potato was almost exactly double the conical flask containing 2 slices. This trend was also seen between the conical flasks containing 4 and 8 pieces of potato. Discussion - The increase in potato pieces meant an increase in surface area, and also the increase in the number of catalase enzymes. Due to the fact that the amount of substrate didn't change (hydrogen peroxide), an increase in catalase caused an increase in the rate of reaction due to more actives sites, causing more gas to be produced. ...read more.

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