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Experimental Question: What effect does substrate concentration have on the rate of enzyme activity?

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Introduction

Name: Utsav Shah THE EFFECT OF SUBSTRATE CONCENTRATION ON THE RATE OF ENZYME ACTIVITY Purpose: The purpose of this experiment is to investigate the effect of substrate concentration over the enzyme activity. This is conducted by using the assay technique. An assay is an analysis performed to determine the presence, absence, quantity or rate of change of a substance. In this assay, the rate of enzyme activity is measured by using stopper test tubes and 6mm disks cut from filter paper. As the catalyst breaks down the hydrogen peroxide into water and oxygen gas, the bubbles of oxygen will force air out and will accumulate to float the disk. Time will be recorded when the disk reaches the surface of the test tube. Experimental Question: What effect does substrate concentration have on the rate of enzyme activity? Hypothesis: If the substrate concentration decreases then the rate of enzyme activity will decrease because it is directly proportional to the substrate concentration. This means that there will be fewer amounts of collisions between the substrate and enzyme molecules resulting in a decrease in enzyme-substrate complexes. Design: Independent Variable: Substrate concentration (Hydrogen Peroxide with following concentrations: 0%, 1%, 2% & 3% are kept constant throughout the experiment) ...read more.

Middle

12. Again, fill the test tube with 10mL of Hydrogen Peroxide (H2O2) and dilute it with 20mL of Distilled Water using the 100mL Graduated Cylinder. This is the 1% concentrated substrate solution. 13. Repeat the procedure from steps 3 to 7 by performing in total of 4 trials and record the time in the observations table. 14. Finally, fill the test tube with 30mL of Distilled Water using the 100mL Graduated Cylinder. Do not add any Hydrogen Peroxide to this solution. 15. Repeat the procedure from steps 3 to 7 by performing in total of 4 trials. 16. If there was no reaction after a minute, record time more than 30s in the observations table. 17. Clean up the work area and return all the materials to their allocated places. 18. After the experiment, each members of the group will calculate the average time for the enzyme activity and construct a bar graph of their averages. The four different substrate concentrations should be on the X-axis and the average time should be on the Y-axis. Observations: Table 1. Qualitative Observations for Different Types of Substrate Concentrations Types of Substrate Concentrations (%) Qualitative Observations 3% (30mL H2O2) Liquid, colourless, fast reaction 2% (20mL H2O2 + 10mL H2O) ...read more.

Conclusion

Therefore, the more substrate molecules are available, the more frequently there is access of active sites of enzyme molecules. Evaluation: There were many sources of errors in this experiment. In the test tube, we found that in one area if there is less substrates, there is less probability to enter in the active site, whereas more substrates will increase the probability to enter in the active site. The faster the reaction, the more hydrogen peroxide decomposed. Therefore, the rate of reaction increases as substrate concentration increases. But there must be a limit to how much substrate is available. At the limit point, when the product is immediately produced, the next substrate should put into the active site and this should go on until the substrate is gone. The only thing that may stop the enzyme activity of saturated substrates would be allosteric inhibition and feedback inhibition. This means that the enzyme will always work until all the substrate is decomposed even though saturated. Having more trials with more concentration of Hydrogen Peroxide would have improved the results. It would help The volumes of the liver extract are slightly different from each other and this may affect the experiment?s results. The volume of the hydrogen peroxide might be changed because it is very reactive and some of the substrate has already broken into water and oxygen. This will somehow influence the experiment results. ...read more.

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