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This is an experiment to examine how the concentration of the substrate Hydrogen Peroxide (H2O2) affects the rate of reaction of the enzyme Catalase.

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Introduction

ALFRED PHOA REF NO: 02651 BIOLOGY T1 PRACTICAL: PLAN THE EFFECT OF THE CONCENTRATION OF HYDROGEN PEROXIDE ON CATALASE IN CARROT CELLS AIMS: This is an experiment to examine how the concentration of the substrate Hydrogen Peroxide (H2O2) affects the rate of reaction of the enzyme Catalase. PREDICTION: I predict that the higher the concentration of the substrate Hydrogen Peroxide (H2O2) the quicker the catalase will hydrolyse and break down the substrate into its simpler constituents. I predict that as the substrate concentration increases, the rate of reaction will go up at a directly proportional rate until the solution becomes saturated with the substrate hydrogen peroxide. When this saturation point Vmax is reached, then adding extra substrate will make no difference to the rate of reaction. HYPOTHESIS: The rate steadily increases when more substrate is added because more of the active sites of the enzyme are being used which results in more reactions so the required amount of oxygen is made more quickly. Once the amount of substrate molecules added exceeds the number of active sites available then the rate of reaction will no longer go up. This is because the maximum number of reactions are being done at once so any extra substrate molecules have to wait until some of the active sites become available. Predicted Graph BACKGROUND INFORMATION: A catalyst is a substance that lowers the activation energy required for a chemical reaction, and therefore increases the rate of the reaction without being used up in the process. There are several factors that affect the action of enzymes: salt concentration, pH, temperature, enzyme poisons, inhibitors, concentration of enzymes and concentration of the substrate and these can affect the collision rate and likelihood of colliding between the enzyme and substrate molecules. ...read more.

Middle

More bubbles produced compared to the first one. 3.0 grams Slow reaction. More vigorous bubbling but still slow Quickest reaction. Most bubbles produced. The bubbles overflowed no result could be recorded 1.) Prepare the dilute solutions of the hydrogen peroxide using the volumes of liquid calculated out beforehand. The measuring cylinders used for distilled water cannot be used for hydrogen peroxide to prevent contamination. * When measuring the volumes of water and Hydrogen Peroxide, the measurement should be taken from a 90-degree angle to avoid parallax error. 2.) Grate out the carrots for a larger surface area for reaction. 3.) Measure out 1.5 grams of the carrots for the reaction 4.) Set up a retort stand to support the boiling tube 5.) Set up another retort stand to support the gas syringe 6.) Clamp the boiling tube with the solution to the retort stand 7.) Put in the grated carrots 8.) Cover the boiling tube with mixture of H2O2 and carrots with a rubber bung with a delivery tube to deliver the gas collected. 9.) Start the stop-clock to time the reaction for 3 minutes 10.) After 3 minutes, measure how much oxygen has been collected and record it 11.) Repeat the experiment at least 3 times for each concentration to get more reliable results. Repeating the experiments several times will help to produce better and more accurate results, as any inaccuracies in one experiment should be compensated for by the other experiments. From these results, a graph can be plotted with concentration on the x-axis and the volume of gas released on the y-axis. BIOLOGY T1 PRACTICAL:ANALYSIS RAW RESULTS TABLE OF O2 COLLECTED WHEN REACTED WITH A % OF H2O2 All results presented to 2 s.f. rounded off to the nearest whole number Concentration of H2O2 (volume) ...read more.

Conclusion

* The water bath was difficult to keep at the constant temperature even if we use an electronic water bath due to heat loss to the surroundings more hot water would have to be added to heat it up again but this is an imprecise method. * There was not a big enough range to do my results and although it could show a decreasing rate of reaction it could not show that the reaction stopped after a certain concentration. * A beam balance with more decimal places would have made the results more exact. * A conical flask with a pressure line could have been used to show how far to push in the bung. This would have been attached to the bung which also connects to the boiling tube to the gas syringe with a delivery tube. The results I obtained have conformed directly to my hypothesis and there is sufficient evidence to support the hypothesis. Although the Vmax was not reached, the general pattern of the graphs plotted conformed to the predicted graph. Further Investigative work > Even more repeats could have been done to improve the accuracy of the results. > The delay problem could be resolved by getting another person to bunge the test tube and start the stop-clock while the Catalase (carrots) were placed into the mixture of H2O2. > A larger range of results could be used for the experiment to clearly present the hypothesis, more concentrations at 40%, 60%, 90% & 95% to show that at the Vmax levels would be reached. By doing these further investigative work, the Vmax can be shown and reducing the anomalies. A better overall result would be obtained by repeating the experiment more times because any errors in one experiment should be compensated for by the other repeated experiments. ...read more.

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