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Investigate the effect of temperature on the activity of catalase (from potato).

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Aim: Investigate the effect of temperature on the activity of catalase (from potato). Introduction: Enzymes are biological catalysts. They speed up metabolic reactions in the body but remain chemically unchanged themselves. Enzymes contain an active site. This is a region, normally a depression or cleft, to which another molecule may bind. This molecule is known as the substrate, and is usually specific to the active site of the particular enzyme, which breaks it down. Substrates will not usually fit into any other active sites other than that of the enzyme it is specified to. This can be explained as a lock and key model, where the lock and key are specific to each other, only, that there are many of the same kinds of lock and key when it come to the enzymes. Just as lock and keys have three-dimensional shapes, proteins are also three-dimensional. Usually, there is only one active site on an enzyme; however there can be more. Some energy releasing reactions in cells produce hydrogen peroxide. This is acidic, and can thus, kill cells. Normally, hydrogen peroxide decomposes to form hydrogen and oxygen: 2H2O2 2H2O + O2 However, this process is very lengthy. There is an enzyme known as catalase in cells which dramatically increases the rate of decomposition of hydrogen peroxide. catalase 2H2O2 2H2O + O2 This type of reaction where a molecule is broken down into smaller pieces is known as a catabolic reaction. In order to investigate the effect of temperature on the activity of catalase, I will record the amount of oxygen released when hydrogen peroxide is broken down. ...read more.


6. Put the potato pieces into a boiling tube and put aside. 7. Measure out 30ml of hydrogen peroxide, using a 50cm3-measuring cylinder. Pour this into a boiling tube. 8. Get the two boiling tubes containing one containing hydrogen peroxide and the other potato. Put them both into the beaker of water once the water has reached the desired temperature (this can be done by heating or adding ice to water). After this, wait until the temperature of the hydrogen peroxide and the water bath are equal. 9. Once the temperatures of the potato and hydrogen peroxide are equal, clamp the boiling tube containing the hydrogen peroxide to a clamp stand. Then add the potato into the test tube Arefin Khan containing the hydrogen peroxide and put bung on top of the test tube, which now contains both potato and hydrogen peroxide, and make sure it is in the beaker of water. 10. Now, measure the water being displaced from the 100cm3 measuring cylinder every thirty seconds using a stop watch. 11. Take readings every thirty seconds for five minutes. 12. Repeat the above steps for different temperatures. Risk assessment: During this investigation, I will use catalase from potato cells to speed up the breakdown of hydrogen peroxide. Hydrogen peroxide is an oxidising agent, as oxygen will be given off during the reaction. This implies that it could help the burning of fires. Due to this, reasonable care must be taken to ensure that the oxygen is not directly exposed to the flame of the Bunsen burner while water is being heated. ...read more.


This is because it is graduated in millilitres. Thus, it will be possible to measure the displacement of water to the nearest 0.5 of a millilitre. Also, the measuring cylinder is not so small that the volume of oxygen produced will be greater than the cylinder can hold within the course of the reaction. The 50cm3 measuring cylinder used to measure the volume of hydrogen peroxide was ideal as the amount of hydrogen peroxide was wasn't too little that it would be inappropriate and also inaccurate to measure with a 50cm3 measuring cylinder, nor was it so large, that it would just about be measured. Boiling tubes are ideal for the reaction to take place in, as the volume of oxygen produced is quite small. Thus, it will be quicker for the oxygen produced to be able to displace the water in the measuring cylinder. With a conical flask, it would take much longer. I also found that the breakdown of hydrogen peroxide at room temperature is very slow (Without a catalyst). No oxygen was given off at all over the period of time I observed the hydrogen peroxide for any reaction. However, I did not test whether this was true for higher temperatures. If it was not, then there is the likelihood of major inaccuracies in the conducting of the experiment. Arefin Khan Source: Background information used during this investigation was obtained from Cambridge Advanced Sciences. Biology 1 - endorsed by OCR: Chapter 3. (Page 42 onwards.) Also, information on variables was taken from concepts learned in AS chemistry: (Salters Horners Advanced Chemistry) ...read more.

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