assignment Flashcards
Title
The effect of hydrogen peroxide concentration on potato catalase activity.
Aim
To investigate the effect of hydrogen peroxide concentration on catalase activity.
Brief Description
Five boiling tubes were set up with different concentrations of hydrogen peroxide. A fixed volume of detergent was added to each boiling tube. A piece of potato was dropped into each boiling tube. After five minutes a ruler was used to measure the height of foam produced in each boiling tube. This was repeated a further two times.
Underlying Biology (up to inhibitors)
Enzymes are biological catalysts that speed up reactions but remain unchanged. Enzymes speed up reactions as they lower the activation energy required to form products from reactants. Activation energy is the minimum energy required for a reaction to occur.
Metabolic pathways are integrated and controlled pathways of enzyme-catalysed reactions within a cell. They are controlled by the presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes.
Induced fit occurs when the active site changes shape to better fit the substrate after the substrate binds. The active site has a high affinity (strong attraction) to the substrate as well as being specific to the substrate. This ensures the reactants are in the correct orientation for the reaction to take place.
Underlying Biology (inhibitors)
Inhibitors decrease the rate of an enzyme controlled reaction. There are different types of inhibitors: competitive inhibitors, non-competitive inhibitors and feedback inhibition.
Competitive inhibitors are molecules that bind to the active site of an enzyme preventing the substrate from binding. This decreases the rate of enzyme reactions. This is a reversible reaction if substrate concentration is increased.
Non-competitive inhibitors are molecules that don’t bind at the active site but change the shape of the active site preventing the substrate from binding. This cannot be reversed by increasing substrate concentration.
Feedback inhibition occurs when the end product in the metabolic pathway reaches a critical concentration. The end product then inhibits an earlier enzyme blocking the pathway and preventing further synthesis of the end product.
Link to Aim
The higher the height of foam, the higher the catalase activity.
Link
In my data the height of foam is an indirect measurement of the rate of catalase activity. In my second source graph the catalase activity was measured as the rate of reaction.
Analysis
In my graph as the hydrogen peroxide concentration increases the average height of foam also increases. An increase in the height of foam means an increase in catalase activity. My second source graph follows a similar trend. As the hydrogen peroxide concentration increases the rate of reaction also increases, meaning the catalase activity increases. However, when the hydrogen peroxide concentration reaches 0.4 mL the rate of reaction stops increasing and stays the same.
Conclusion
In conclusion, as hydrogen peroxide concentration increase catalase activity also increases. However, my second source shows that catalase activity will eventually stop increasing as hydrogen peroxide concentration continues to increase.
Evaluation
The results of my experiment were reasonably reliable as I repeated the experiment 3 times and found an average height of foam for each hydrogen peroxide concentration. My results for each repeat were similar and created a trend similar to my second source suggesting my results are reliable.
I also made sure my results were valid by using a control. My control was measured when the hydrogen peroxide concentration was 0 vol. This proved that it was the concentration of hydrogen peroxide that was affecting the height of foam and therefore the catalase activity making my results more valid.
However, to make my results more valid I could’ve used water baths at a fixed temperature to keep the boiling tubes at a constant temperature throughout the experiment. This would ensure that varying temperatures aren’t affecting the catalase activity in my experiment, making my results more valid.
