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Investigating if concentrations of catalase on a solution of hydrogen peroxide have any effect on the amount of oxygen evolved in the chemical reaction of hydrogen peroxide decomposing to become oxygen and water

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Introduction

GCSE Coursework Biology- 'Bubble Trouble' Planning Investigating if concentrations of catalase on a solution of hydrogen peroxide have any effect on the amount of oxygen evolved in the chemical reaction of hydrogen peroxide decomposing to become oxygen and water. The reaction is written: hydrogen peroxide --> Oxygen + Water H2O2 --> O2 + H2O Catalase catalyses this reaction and supposedly speeds it up by roughly 10000 times. I am going to keep the levels of hydrogen peroxide constant and vary the amount of catalase. List of apparatus 5 sets of 1mm thick potato discs containing the enzyme catalase. In the numbers 2,4,6,8 and 10 (3 lots of each, creating 15 lots of potato discs each set) 15 test tubes Hydrogen peroxide (vol.20) (5 ml in each test tube) pH9 Buffer Solution Water bath set to 40�C Detergent Stopwatch Razorblade Ruler Method Some cylinders of potato will be cut into 60 discs of 1mm thickness using a razorblade. Next I will take 15 test tubes and fill them with 5ml of pH7 buffer solution. In 5 of the test tubes I will add 3 potato discs. In 5 other test tubes I will add 6 discs and in the last 5 test tubes I shall add 9 potato discs. ...read more.

Middle

The reason why an enzyme is so specific is because it is a globular protein with a distinct three-dimensional shape which corresponds to the molecule or molecules it reacts with (substrate(s)). When an enzyme catalyses the reaction of its substrate it forms an association with it called an enzyme-substrate complex. This is possible because quite a large part of enzyme called the active centre matches the shape of its substrate. So when an enzyme and its substrate collide at the right orientation they become attached at the active centre. The enzyme and substrate can now interact in a way that allows the substrate to react in a much more efficient way and the products of the reaction are formed. When this happens they detach from the active centre and the enzyme is left unchanged to go and react with another substrate molecule. This can be repeated extremely quickly especially in the case of catalase. Each molecule has the potential to combine with up to 10000 molecules of hydrogen peroxide per second. The mechanism of enzyme action I have just described is known as the Lock and Key Hypothesis with the enzyme being the lock and the substrate being the key. However this concept is not fully helpful, as the 'lock' and 'key' are not static structures. ...read more.

Conclusion

When this happens they detach from the active centre and the enzyme is left unchanged to go and react with another substrate molecule. In the terms of my results, roughly twice the number of enzyme 'locks' have been introduced to the same amount of hydrogen peroxide 'keys', meaning the locks and keys can join at twice the rate previously. This means that double the amount of reactions take place in half the time previously. For example in my results when I used 4 potato discs, it took 188.6 seconds for 2ml of oxygen to be collected, but when I doubled the number of discs (and therefore the amount of the enzyme) it only took 92.3 seconds - that's roughly half the time. I can back up this statement by concentrating on the class results above: When group 3 used 4 potato discs, it took 187 seconds for them to collect 2ml of oxygen, but when they doubled the number of potato discs, and therefore the amount of enzyme, it only took 94 seconds - roughly half the time. I therefore conclude that by doubling the amount of catalase to a solution of hydrogen peroxide, the rate of the reaction will double, therefore meaning that the time taken to collect a given amount of oxygen will halve. ...read more.

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