Experiment to investigate the effect of varying surface area hence varying the amounts of Catalase on the breakdown of Hydrogen Peroxide.

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Voirrey Fermor

21/03/03

Experiment to investigate the effect of varying surface area hence varying the amounts of Catalase on the breakdown of Hydrogen Peroxide

Aim: to investigate the effect of the amount of catalase and the breakdown of hydrogen peroxide.

Hypothesis: Hydrogen peroxide will breakdown to oxygen and water in the presence of catalase. The enzyme catalase carries out the following reaction:

2H2O2         2 H2O (l) + O2 (g)

Catalase is an enzyme, enzymes are globular proteins that have tertiary structures with hydrophilic R groups that form a precise active site which is substrate specific to hydrogen peroxide substrate.  Hydrogen peroxide substrate and the catalase enzyme join to form the enzyme substrate complex.  Temporary bonds are formed until the active site of the enzyme splits the toxic substrate hydrogen peroxide into two harmless products, oxygen and water.  This process happens naturally but slowly, catalase lowers the activation energy so the reaction happens more quickly without the need for more heat which can damage living cells.  The reaction with catalase happens in living creatures as hydrogen peroxide is a toxic waste product of certain metabolic reactions such as respiration.  Hydrogen peroxide is used by neutrophils to kills bacteria after it has engulfed it as hydrogen peroxide is a powerful oxidiser and therefore punches holes in the cell wall of the bacteria.  I found this information on  and biology one.

I predict that the higher the amount of catalase exposed to the hydrogen peroxide the faster the rate of reaction. As the surface area double the amount of gas produced should double as double the amount of catalase enzmes can work to breakdown the hydrogen peroxide.  According to biology one each catalase active site can breakdown 107 hydrogen peroxide molecules per second, if more active sites are exposed more compound can join and be split by the catalase enzyme. The reaction will increase with increasing enzyme concentration when molecules of hydrogen peroxide are freely available. There will be an optimal point at which all the enzyme active sites are filled and operating at each amount of catalase.  At this point the reaction will stop producing more gas when the hydrogen peroxide has been broken down into water and oxygen, water is unaffected by catalase.

Plan:  the input variable that I will be changing is the surface area exposed to the hydrogen peroxide.  I will vary the enzyme concentration by making cuts into the potato chip of 40mm which naturally contains the Catalase.  Therefore I will have one chip with no cuts, a second cut in half and a third cut into thirds and so on. A cut increases the surface area but the weight and proportion of change stay the same.  The greater the surface area, the greater the enzyme concentration.  I will measure the volume of oxygen given off by the reaction.  To check if the gas is oxygen I will see if the gas can light a glowing splint.  I will measure the volume of gas but I will discount the volume of air displaced by the hydrogen peroxide when it is put in.  This will be done at 30-second increments of time starting at zero until 210 seconds, my preliminary work showed that shorter increments such as every 10 seconds were hard to keep up with and the results did not shown many changes.  The measurements at different times will show rates of reaction of each amount of surface area.  I will cut the potato chip into smaller and smaller pieces therefore increasing the surface area I will use the formula for finding the surface area of a cylinder.  

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2πr2  + 2rl (+2πr2) (+2πr2)….

I will assess my results by using a mathematical method called Product moment correlation coefficient (PMCC).  This will show how closely correlated my results are and therefore show how reliable they are.  The result of the PMCC equation will be between 1 and –1.  The closer to one the closer the results are correlated i.e. how closely they follow a pattern.  Below 0.7 would show a weak correlation.

This is the formula:

Σ×y-ΣxΣy

       n

(Σx2 – (Σx) 2) (Σy2 - ...

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