An investigation to see the difference in the rate of reaction when catalyse is added to hydrogen peroxide at different concentrations.

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Tuesday 3rd March                                                                             William Bowles.                                                                            

Biology plan- an investigation to see the difference in the rate of reaction

When catalyse is added to hydrogen peroxide at different

Concentrations.

I am doing an investigation to look at the difference in the rate of breakdown when catalase is added to hydrogen peroxide when the hydrogen peroxide is of different concentrations. When catalase is added to the hydrogen peroxide then a breakdown takes place and water and oxygen are produced. When I say concentrations I mean with a different ratio of hydrogen peroxide to distilled water.  I am doing this investigation to find out how the rate of oxygen produced will differ. The reason why these two substances do react is because enzymes are large proteins that speed up chemical reactions. Catalase is an enzyme that is specific for the breakdown of hydrogen peroxide to water and oxygen. So when catalase is added the breakdown starts immediately. The following information is quoted from Encarta: In their globular structure, one or more polypeptide chains twist and fold, bringing together a small number of amino acids to form the active site, which is where the reaction takes place. Enzyme and substrate fail to bind if their shapes do not match exactly. This ensures that the enzyme does not participate in the wrong reaction. The enzyme itself is unaffected by the reaction. When the products have been released, the enzyme is ready to bind with a new substrate. So catalase couldn’t react with anything other than hydrogen peroxide because the two of them wouldn’t fit together. Yeast contains catalase, all the cells contain catalase because it is needed to get rid of the H2O2 which is made during the chemical reactions that release energy in respiration.

 The part in purple is the hydrogen peroxide and the part in blue is the catalyse. You can see that when they lock together the breakdown takes place and oxygen and water is formed.

The input variable for my investigation is the concentration of the hydrogen peroxide. I am going to change the ratio of water I add to hydrogen peroxide. I am not changing any other factors.

H202                   O2 + H2O

The volume of O2 is what I am measuring. (The rate at which it is produced).

I predict that the results of my investigation will be that the more diluted the hydrogen peroxide is, the slower the breakdown will be. By this I mean oxygen will be produced at a slower rate. The reason I think this is because the higher the concentration of hydrogen peroxide is the quicker the breakdown will be. This is because the higher the concentration is, the more hydrogen peroxide molecules in it and it makes it quicker

for the catalase to react with it. The more concentrated the substrate is, the greater the rate of reaction will be. This is because increasing the concentration increases the

molecule numbers and so that increases the frequency of collisions between particles and, therefore, increases the rate of break down. This also explains why the greatest rate of reaction is usually as soon as the reactants are mixed ( even more so because of concentration levels). The lower the concentration the longer it will take to react because collisions happen less frequently.  Here is a predicted graph to support that. As each reaction proceeds the concentration of H202 decreases because more and more molecules are being broken down. The rate of reaction slows down because there are less and less substrate molecules for catalase to break down.

                                                  graph

Variables that could affect this investigation.

Temperature. – If the room temperature is quite warm then you will find that the breakdown rate will increase, there for the rate of oxygen will increase as well. The reason this happens is because when it is warmer the molecules move about more so collisions occur more frequently and catalase will be able to break down the substrate molecules faster. So if it was cold then the molecules would move about slower and if very cold then they will barely move at all. This makes it more difficult for the catalase to break down the substrate molecule at a fast rate.

Concentration of H2O2. – If the concentration of H2O2 was very high then the catalase will be able to break it down faster. This is because if there is a high concentration of H2O2 then there are more H2O2 molecules for the catalase to break down so the catalase can collide with a H2O2 molecule quicker and then move on to the next one. So this means the rate of oxygen produced will increase as well. If the concentration was low then the catalase would find it harder to find H2O2 quickly so the rate of oxygen produced would be low.

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Concentration of catalase (yeast). – If the concentration of catalase is high then there will be more catalase molecules which means they can get round the breaking down of the H2O2 quicker. This means the rate of oxygen produced will be higher if the concentration of catalase is high, and be low if the concentration was low.

 

Volumes of H2O2. – if you have a large volume of H2O2 and you mix it with catalase then the break down rate will be faster than a small volume. This is because if there is a larger volume then ...

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