Results
Graph
Conclusion
Hydrogen peroxide decomposes to form oxygen and water; this reaction is catalysed by the enzyme catalase found in yeast. This is shown by the equation below:
Catalase
H202 O2 + H2O
The reason the rate of reaction increases is because the enzyme lowers the level of activation energy required by the reactants in order to react upon collision. This results in more successful collisions and an increased rate of reaction. Enzymes achieve this in two ways. When breaking down molecules it puts strain on the bonds holding the molecule together so it is easier to breakdown. When joining molecules, enzymes bring together the molecules to make it easier for them to be joined.
As shown by the graph the rate of reaction increases as the mass of yeast is increased. This shows that an increase in concentration of an enzyme increases the rate of reaction. This is because there are more enzymes available for the substrate to collide so it is more likely a successful collision will take place and an enzyme-substrate complex will form thus increasing the rate of reaction.
Evaluation
I feel my results are fairly accurate however I think that the relationship between the rate f reaction and the enzyme concentration is more linear then the graph and the trend line suggest; this is something I would like to investigate I could also make results more reliable if I were to repeat the experiment several times (at least two more times).
There were some inaccuracies in my method as when I placed the bung in the conical flask there was an instant for which gas could escape. I could resolve this problem by using different apparatus as shown in the diagram below:
This diagram shows how the Hydrogen Peroxide can be syringed in to the flask which is sealed so no gas can escape.
The use of a thermometer will monitor any temperature change of the solution throughout the experiment which may result in there being an unfair test due to its impact on enzyme activity.
Using a syringe instead of a cylinder helps avoid the problem of air bubbles in the measuring cylinder created as it is submerged in the water bath.
If I were to use a larger volume syringe than the 100 cm3 measuring cylinder to collect the gas I would be able to see more accurately when final volume gas was produced because sometimes this was hard to do when the reaction was going so fast.
I could extend the experiment by testing higher masses of yeast in order to see if this relationship between rate of reaction and enzyme concentration increased forever or whether it is ever limited by the substrate concentration. However to do this I would have to decrease the volume of hydrogen peroxide used because this created far to much gas thus I would need to scale it down.
