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Investigating the effect of substrate concentration on the enzyme catalase.

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Introduction

Investigating The Effect of Substrate Concentration On The Enzyme Catalase Aim: this is an investigation to examine how the concentration of Hydrogen Peroxide (H2O2 ) affects the rate of reaction of the enzyme Catalase, where carrot will be the supply of catalase. Enzymes are proteins and thus have a specific shape. They are therefore specific in the reactions that they catalyse - one enzyme will react with molecules of one substrate. The site of the reaction occurs in an area on the surface of the protein called the active site. Since the active site for all molecules of one enzyme will be made up of the same arrangement of amino acids, it has a highly specific shape. Generally, there is only one active site on each enzyme molecule and only one type of substrate molecule will fit into it. Enzymes are catalysts. Catalysts speed up chemical reactions that would normally happen very slowly. Enzyme molecules have a complicated three-dimensional shape due to the particular way the amino acid chain that makes up the protein is folded. This tertiary protein structure gives the enzyme its catalytic ability. Cells contain many enzymes. Without the enzymes in our cells, reaction would be too slow to maintain life. When chemical reactions take place, bonds are destroyed or created. The energy that is needed is called activation energy. Activation energy is the energy needed to bring molecules together so that they will react with each other. Instead of supplying energy, enzymes reduce the height of the energy barrier and therefore reduce the activation necessary for a reaction to take place. Enzymes only act on one particular or group of substances. They are therefore said to be specific. The shape of the molecule, especially the active site, is linked with this specificity. This can be explained by the lock and key hypothesis. Specificity is important as it prevents random disorganised reactions taking place, thus there is more control. ...read more.

Middle

Method: Set up apparatus as shown on the next page. * Firstly, make sure the gas burette is filled up fully, and put it in a beaker full of water, held by a stand and clamp. * Grate the carrot, so the mass of the carrot is the same throughout the experiment. Make sure the mass is 4grams. * Add the 4grams of grated carrot to the test tube. * Next, add 10ml of 1% concentrated hydrogen peroxide to the test tube using a syringe. * Add the bung with the delivery tube on the test tube and make sure you put the delivery tube in the gas burette, and time how long it takes to collect 10cm3 O2 in the gas burette. Repeat the procedure at least another two times. * Repeat this method also for 1.5, 2.0, 2.5 and 3.0% concentrated hydrogen peroxide solutions. * Also, check ph levels of each experiment, by using litmus paper. I will try to repeat each concentration at least thrice so I can get an average and make my results more reliable because by replicating observations increases the reliability of the results. Hydrogen peroxide can be corrosive if strong, and an irritant to the skin and eyes. It should not be swallowed. It can corrode clothes and irritate the skin if not washed off thoroughly. Goggles should be worn to protect the eyes. Contact with the skin should be avoided and clothing should be protected thus by wearing a lab coat and gloves you are protecting your skin from any irritating chemical. You should also clean up any spills. The workplace should be tidy and any equipment not needed should be put away as it can get in the way. You should avoid handling, inhaling or contact with the skin wherever possible, so by using a spatula and syringe you are not touching the substrate or source of enzyme. ...read more.

Conclusion

Specific amounts could be measured much more precisely. I would use a gas syringe or manometer instead of a burette because connecting the delivery tube to the burette takes a lot of time whereas by using a gas syringe, it would be set up and you would have to connect the delivery tube to the gas syringe before the experiment would start. Also by using different equipment it may give a variety of results and I would be able to compare the results and presume which instrument is more reliable and accurate. I did not use a water bath, so if I repeated the experiment I would use a water bath to keep the temperature constant because in my experiment I was not able to control the temperature because I kept the temperature at room temperature but the temperature could have changed without my7 knowing even though it was checked at regular intervals. By using a water bath I would keep the temperature constant and therefore be controlling on of my variables. I would also use a buffer solution to keep the ph levels the same, I did not use it this time because time was a key factor and by doing this I would have lost valuable time. I did three repetitions for each concentration to make my results more reliable by working out an average. However if I had more time I would have done more repetitions to increase the reliability of the results. If I repeated this experiment again I would do a minimum of 5 repetitions. I measured the time taken for 100mm3 of oxygen to be produced. Instead of this I would measure how much oxygen is produced in a certain time period for example one minute. I would also increase the volume of the hydrogen peroxide because as you increase the substrate more enzyme-substrate complexes are being formed. After evaluating my experiment I can say that my results were reliable to a certain extent and that my prediction was correct, and this was proved in my conclusion. Hassan Patel ...read more.

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