An investigation into how the amount of oxygen is produced by changing one variable effects the decomposition of Hydrogen Peroxide in the presence of the enzyme.

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INTRODUCTION:

An investigation into how the amount of oxygen is produced by changing one variable effects the decomposition of Hydrogen Peroxide in the presence of the enzyme.

AIM:

To investigate the affect of varying the concentration of H2O2 in a catalyse reaction of an enzyme.

THEORY:

Enzymes exist in all living things. They are known as Biological Catalysts as they dramatically increase the rate at which reactions occur within living organisms, without being ‘used up’ or effecting the reaction in any other way.

In this investigation I intend to explore the one of the factors that will affect the rate of enzyme catalysis. My research from textbooks and the Internet suggests that this depends on several factors; temperature, pressure, pH and concentration of H2O2. After research and careful consideration, I have decided to first look at how a change in H2O2 concentration could affect the rate of reaction.

Enzymes are proteins of a very specific shape. They work by capturing the molecules that they react with (called their "substrate"). The reaction happens and then the products of the reaction are released. The enzyme is then free to react again.

Vital to this is the shape of the enzyme. It must exactly fit with the substrate like two pieces of a jigsaw puzzle. It's also often described as a "key" (the substrate) fitting into a "lock" (the enzymes active site). Hence giving the theory the name, “The Lock And Key Theory.”

 Anything that alters the shape of the enzyme alters the shape of the active site and so the substrate cannot fit in and the enzyme no longer works. Changes in temperature and pH have this effect. This is called denaturation.

There is some evidence, however, that not all active sites are rigid receptors for enzymes. In some cases, the active site changes its shape to fit “snugly” around the substrate once it enters the active site. This is known as the Induced Fit.

                                 

Of more than 1000 known enzymes, each has a characteristic 3D shape, which allows it to recognise and bond to certain substrates. When an enzyme is denatured, the active site loses its unique shape and can no longer fit together with its substrate due to heating.  The enzyme does not regain shape when cooled. The active site is too denatured to allow the bonding of the substrate. Therefore no reaction.

THE COLLISION THEORY simply states that when there are more substrate molecules, the more collisions there will be and so the rate of reaction will increase. However, when the substrate molecules begin to out-number those of the enzyme, the collisions will decrease and so will the rate of reaction.

Enzyme activity is poor at low and high temperatures but is quite vigorous at around 25 to 35 0C.  Different enzymes work better at different pH values.

Examples of enzymes can be found in the digestive system where they break down large molecules of starch, protein and fats into smaller molecules, which can be absorbed by the blood stream. Amylase is the enzyme that breaks down starch into glucose; Proteases break down into amino acids and lipases breaks down fats to fatty acids. In these examples, the enzymes are the ‘lock’ and glucose, protein and fats are the ‘keys’.

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Catalyse is a type of enzyme that is very good at speeding up the rate of reactions. It is different in that it has different substrates to amylase:

AMYLASE

Starch                 glucose                               (C6 H12 O6)n                  C6 H12 O6

CATALASE

Hydrogen peroxide            water + oxygen               2H2O2                2H2O +O2

Catalase is found in all ...

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