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Find out how a certain factor that is changed will affect the reaction rate of enzymes

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Investigating Enzymes By Hannah Robinson Aim: The aim of this experiment is to find out how a certain factor that is changed will affect the reaction rate of enzymes. Enzymes are globular proteins which act as biological catalysts. A catalyst is a molecule which speeds up reactions without being used up itself. All globular proteins have a tertiary structure, which makes them very easily altered by pH and temperature. Enzymes are different to other globular proteins as they have an active site to which other molecules can bind. The molecule is called the substrate for that enzyme. The shape of the active site allows the substrate to fit perfectly and be held in place by temporary bonds between the substrate and the R groups of the enzymes amino acids. An amino acid The combined structure is called the enzyme-substrate complex. The active site for all molecules of one enzyme is made up of the same arrangement of amino acids, and therefore has a highly specific shape. There is usually only one active site on each enzyme molecule and only one type of substrate molecule that will fit into it. The enzyme is said to be specific for that substrate. This is known as the lock and key hypothesis. The enzyme may catalyse a reaction in which the substrate molecule is split into two or more molecules. It may also catalyse the joining of two or more molecules together as when making a dipeptide. Interaction of the R groups of the enzyme and the atoms of the substrate can break or encourage the formation of bonds in the substrate molecule. When the reaction is complete, the product or products leave the active site. The enzyme is unchanged by this process, so it is then available to receive another substrate molecule. Some research on enzymes has suggested that the active sites of enzymes may not be exactly the right shape for the substrate to begin with. ...read more.


I will pour the 10% hydrogen peroxide into the conical flask and quickly put the bung in to it. I will then start the stop clock immediately and record the amount of gas produced every 30 seconds. Results: Using 5cm� of 20% hydrogen peroxide - How much oxygen is released in 120 seconds Length of potato chip (cm) Gas produced (cm�) Time (seconds) 30 60 90 120 3 1.4 2.3 3.2 3.5 4 0.5 2.0 3.5 4.4 5 1.6 3.0 4.0 5.5 The 4cm potato chip seemed to give an odd result on 30 and 60 seconds as the number should be higher than that of the 3cm chip but lower than the 5cm chip because in the difference in surface area for the reaction to take place. This may have been because of a blockage in the delivery tube or not cleaning the equipment thoroughly. Using 10cm� of 20% hydrogen peroxide - How much oxygen is release in 120 seconds Length of potato chip (cm) Gas produced (cm�) Time (seconds) 30 60 90 120 3 1.3 2.6 3.5 4.5 4 1.0 1.5 3.7 4.5 5 3.0 4.5 6.5 8.3 The results give a wider range with 10cm� of hydrogen peroxide and with 5cm chips of potato. Using 10cm� of 20% hydrogen peroxide and 5cm potato chips I will repeat the experiment recording the gas produced every 30 seconds for 5 minutes to find out if this would be a suitable time span for my experiment. Time (seconds) Amount of gas produced (cm�) 30 1.2 60 3.2 90 5.1 120 7.2 150 9.0 180 11.0 210 12.7 240 14.3 270 16.2 300 17.7 This seems a suitable time span for my experiment as I get a good increase in gas released. Conclusion: From these tests I have decided to use 10cm� of 20% hydrogen peroxide, 5cm potato chips cut into 1cm chips, and conduct my experiment for a total of 5 minutes, recording the gas released every 30 seconds. ...read more.


This suggests that the equipment had some remains of other enzymes in, or possibly that the delivery tube still had gas in it from the last experiment. Once I have removed the anomalous results my other trials are more accurate. They are similar in number indicating that the results are reasonably accurate. If I repeated this experiment I would take much greater care in washing the equipment between each trial and also ensuring that the delivery tube did not contain any gas before each experiment was begun. This would ensure more reliable results as no factors from previous experiments would effect the experiment. It also may be more accurate to use a gas syringe to measure the oxygen produced. This would conquer the problem of creating pressure in the delivery tube and should therefore produce more reliable results, although this method may not be as accurate, as the measuring units on a gas syringe are larger than on a burette. If I had had more time I would have taken more care to ensure everything was exactly the same in each experiment. I would have checked the temperature with a thermometer before each trial, to ensure the same conditions, and I would have ensured the buffer was properly dissolved. This would make my results more reliable as the conditions would have been exactly the same for each trial. My conclusion may not be entirely accurate as I did not have the resources available to me to test the potatoes in other ways to try and find out about their individual properties. I also could not easily find information on this subject. It is also difficult to know if all the potatoes of a certain species have been treated in the same way and so if I used a different make of the same types of potatoes, it may produce different results. If I had had more time I could have tried to investigate some of these other factors. Hannah Robinson 1 ...read more.

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