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The effect of substrate concentration on the activity of catalase on hydrogen peroxide.

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Introduction

The effect of substrate concentration on the activity of catalase on hydrogen peroxide Planning Aim: This is an experiment to examine how the concentration of the substrate hydrogen peroxide affects the rate of reaction of the enzyme catalase. Hypothesis: If substrate concentration is increased, the rate of reaction will increase at a directly proportional rate until the solution becomes saturated with the substrate hydrogen peroxide. Adding anymore substrate after this saturation point is reached will make no difference. As more substrate is added the rate of reaction increases steadily because more of the actives sites of the enzyme are being used which result in more reactions taking place. So the necessary amount of oxygen is produced more efficiently. Once the amount of substrate molecules added exceeds the number of active sites available then the rate of reaction will no longer increase. This is because the maximum number of reactions are occurring at once so any extra substrate molecules have to wait until some of the active sites become available. Background Information Enzymes: All enzymes are globular proteins and within the cell they have two main roles. 1) They act as highly specific catalysts, greatly speeding up chemical reactions, which should otherwise be extremely slow. 2) They provide a mechanism whereby individual chemical reactions can be controlled, the available quantity of an enzyme determining the rate of the corresponding reaction. Figure 1 shows the specificity of an enzyme's action arises because each enzyme has a definite three-dimensional shape, which is complementary to that of its reacting molecules, or substrate. ...read more.

Middle

Safety: All biological activity have to be treated with care. * Wear safety goggles throughout the experiment to protect eyes. * Tie long hair back to prevent it getting in the way * Hydrogen peroxide is a toxic substance, if it makes contact with skin wash immediately. * Take care when using knife to avoid any accidents. * Never place fingers in mouth or eyes after using chemicals. * The enzyme catalase will be used in the form of celery. However, the fact that all biological activity have to be treated with care must be taken in to account. * Concentrated solutions are unstable and the pure liquid may explode violently if heated to a temperature above 100?C. * If too much pressure buils up then the syringe will come out and break. In order to prevent this, two separate parts of the syringe should be tied together. The bung will be loosend to release pressure. * Extra care needs to be taken in the laboratory because glass apparatus is being used. Buffer solution does not keep well due to mould growth. Once the tests have been carried out do not dispose the experimental substances down the sink. Once the whole experiment is conducted, transfer the contents into an empty beaker. The substance can now be poured down the sink as it is now only water. It is important that the content is not disposed of until certain the experiment is completed because if not it can be dangerous as gas may still be given off and the H2O2 is corrosive. ...read more.

Conclusion

Unfortunately, it is impossible to keep all measurements exactly the same with the basic equipment and conditions I had. For example I found it is impossible to precisely measure out exact amounts of hydrogen peroxide each time because the scale of the measuring cylinder shows the measurements to the nearest 1mm� whereas I needed it to be correct to the nearest mm�. There was also a delay between pouring in the H2O2 and starting the stop watch because only one procedure could be carried out at a time. However this should affect all the results for each individual test I conducted and therefore should not make any significant difference to the overall results. Further Improvement: My experiment could be improved in numerous ways. The experiment could be repeated more times to delete any anomalies and to produce a more accurate overall result. After carrying out my investigation I came to the conclusion that using catalase founded in celery made it difficult to measure precisely the desired amount of catalase. I did however crush the celery into minute equal sizes to ensure the enzyme concentration was as equal as it could be. For further investigation I believe a source of catalase from yeast would be ore appropriate as it is easier to use and determine the desired amount of yeast catalase by simply measuring it off. The problem of the delay between pouring in the H2O2, placing the bung securely on the test tube & starting/stopping the stop watch could have been limited by using another person to start & stop the timer when the H2O2 was being poured into the tube. ...read more.

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