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Enzymes Coursework (GCSE)

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Enzymes Coursework Enzymes are biological catalysts, they are found inside every living cell and speed up chemical reactions. They are made up from a long chain of amino acids folded in upon itself until it has a cleft in the exact shape and size of the molecule it was designed to act on, this makes enzymes specific to one reaction - an enzyme with an active site the shape of starch molecules can't act upon hydrogen peroxide molecules. This is the lock and key hypothesis. Only the right key will fit the lock, only the right enzyme will act on the substrate. The catalase enzyme will help break down hydrogen peroxide into water and oxygen, this reaction would take place anyway but it would not happen as fast and would require more energy - the enzyme speeds up the reaction and reduces the required amount of energy. The lock and key hypothesis takes place when the enzyme comes into contact with the specific substrate and the substrate slots into the active site to form an enzyme/substrate complex, here the enzyme speeds up the process of breaking up the substrate. The enzyme/substrate complex:- The Lock and Key Hypothesis:- There are many variables that will affect the speed of this reaction, one of them is the temperature - different enzymes will have different optimum temperatures that they work at, this depends on where the enzyme is to be found. ...read more.


Using the forceps I will drop the required amount of discs (6 for the first three experiments, 9 for the next three experiments, 12 for the last three experiments) into the boiling tube containing the hydrogen Peroxide, I will give this a quick swirl then place it back in the beaker full of water at 37�c and push the bung on the end of the delivery tube into the top of the boiling tube, at the same time starting the stopwatch. Every 30 seconds for 5 minutes I will record how much gas has collected in the upside down measuring cylinder. I will repeat this experiment as many times as I need to. To make sure I am performing a fair test I will make sure that all the measurements I carry out are as accurate as possible - the water will be at exactly 37�c in every experiment, every potato core will have been cut with the same corer and every disc will be 1mm thick, I will use 10cm� of Hydrogen Peroxide in each experiment. Doing this will make sure that all the variables remain constant apart from the amount of potato disks used - which is what I am investigating - making this a fair test. Here is my equipment Layout In this experiment I will be very careful in my measuring of the Hydrogen Peroxide, the size of the potato discs and the temperature of the water as these are variables I will be keeping constant. ...read more.


I did not have the required equipment for any of these improvements. Other causes for my anomalies could be that if the Hydrogen Peroxide (H2O2) had been left out for a while it could have degraded. This would dilute it, reducing the chance of a Hydrogen Peroxide molecule colliding with the enzyme, slowing down the reaction. Also the potato I used could affect the reaction rates. In all my experiments I used the same potato but I did each set of experiments (6 discs, 9 discs and 12 discs) on separate days so the potato was ageing. The age of the potato affects the amount of enzymes it contains, the older it is the fewer enzymes. Therefore it is likely that there were slightly fewer enzymes in the potato disks I used in the nine discs experiment than the 6 discs experiment and slightly fewer enzymes in my 12 discs experiment than in my 9 and 6 discs experiments. The fewer the enzymes the fewer active sites available and the less chance of collision between enzyme and substrate. This produces a slower reaction. To extend my experiment I could find the temperature at which the enzymes stop catalysing the reaction either due to denaturing or lack of energy due to insufficient heat. To do this experiment I would use a set amount of potato disks and change the temperature of the water bath, recording the amount of gas collected in 5 minutes for a range of temperatures between 10�c to 40�c. ?? ?? ?? ?? Rowan Griffin 10JH 1 Biology Coursework ...read more.

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