Apparatus
- Tweezers- will allow me to dip filter paper into catalase
- Hole punch- to create small discs out of filter paper
- 1 syringe- will allow me to insert precise amounts of hydrogen peroxide into the beaker
- 100 ml beaker- will contain Hydrogen peroxide.
- 250 ml beaker
- 1 test tube
- 1 test tube holder
- 1 filter paper- from this filter paper i will make discs which will
- 1 stop clock- to measure the amount of time it takes for the filter paper discs to rise to the surface of the water.
Method
- Collect all equipment.
- Collect 100 ml of hydrogen peroxide in the 100 ml beaker.
- Place 5ml catalase into the test tube.
- Use the punch to create small discs out of the filter paper.
- Put 100% hydrogen peroxide into each of the three specimen tubes in accordance to the dilution table.
- Use tweezers to dip filter paper in the catalase for precisely 5 seconds
- Drop filter paper into specimen tubes when it touches the bottom start the stop clock and time how long it takes to reach the top. Repeat this four times for every hydrogen peroxide concentration as this will produce more accurate results as any anomalies should be compensated for by the repetition.
- Plot results in a table like the one below.
To ensure this is a fair test all variables except for the concentration of Hydrogen Peroxide must be kept the same for the entire experiment.
When recording the time it takes for the filter paper to rise to the surface of the hydrogen peroxide the specimen tube should be looked at from an angle of 90 degrees to it to avoid any parallax error.
Predictions
I predict that there will be a positive correlation between the concentration of hydrogen peroxide and the rate of reaction of catalase.
Results
Analysis
From looking at the graph i can see that there is a positive correlation between the rate of reaction of catalase and the concentration of substrate in this case this is hydrogen peroxide.
When the concentration of Hydrogen Peroxide is increased, the rate of reaction also increases at a directly proportional rate from 20% until 80% concentration of Hydrogen Peroxide. When the concentration is doubled from 20% to 80% the rate of reaction goes up 0.04 to 0.11. From 80% onwards the rate of reaction slows this could be due to the enzymes active sites being saturated with hydrogen peroxide.
This is bearing in mind that the measurement made for 40% hydrogen peroxide was an outlier as it did not fit the general trend explained previously. It has therefore been excluded from the results.
Conclusion
To conclude from this investigation i have found that there was a positive correlation between these 2 factors: the rate of reaction of catalase and the concentration of substrate (hydrogen peroxide).
The relationship however the relationship was not as straightforward as this; after the reading 20% on the graph the rate of reaction increased until about 80% when it began to slow again. As explained previously the rate of reaction of catalase slows when its active sites are saturated with hydrogen peroxide this explains the decrease in the rate of reaction seen from 80% to 100%.
I do not feel as though i can draw a sound scientific conclusion based upon the data i have collected and analysed because; firstly due to the low number of repeats for each experiment it would be possible for a single outlier to skew the average result to the extent that it does not fit the line of best fit, secondly several of the ranges over lap indicating unreliability, and thirdly the fact that one result at 40% concentration did not fit the trend made me question the reliability of the rest of the results.
Evaluation
To make this experiment more accurate, I repeated it four times and then created an average of the four results in plotting the graph. I attempted to keep all variables such as Temperature and hydrogen peroxide concentration the same for all the trials. However, it is not possible to create exact conditions for each trial experiment. For example:
a) There was a slight delay between starting the stop clock when the filter paper hit the bottom of the specimen tube and stopping the stop clock when it reached the surface of the water.
b) There is also no way of ensuring that all volumes of Hydrogen Peroxide are the same.
c) There is also no way of ensuring temperatures, exposure to light and many other factors remain the same although i doubt whether this would make a great difference in the results it is still possible that this difference could have a profound effect and therefore skew the data.
In order to improve the reliability of this investigation i could carry out more trials this would preventing outliers from skewing the data.
I could have also used a greater number of concentrations of hydrogen peroxide this would have improved the reliability of the line of best fit may have shown me what the maximum possible rate of reaction was before it began to slow.
It would have also have been possible for me to have another person involved in my experiment whose job it would be to start and stop the stop clock. This would have meant a better reaction time and therefore more reliable results. Alternatively we could have deducted 0.1 seconds from the time calculated. This 0.1 seconds would represent the delay in amount of time it took us to start and stop the stop-clock.
