An Investigation on the Rate of Reaction of the Enzyme Catalase on the Substrate Hydrogen Peroxide.

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An Investigation on the rate of reaction of the enzyme Catalase on the substrate Hydrogen peroxide.


Aim: To investigate the rate of the effect of Catalase on hydrogen peroxide.

This investigation will be carried out to investigate the rate of reaction of the enzyme catalase on the substrate hydrogen peroxide. Enzymes are biological catalysts, which speed up the rate of reaction without being used up during the reaction, which take place in living organisms. They do this by lowering the activation energy. The activation energy is the energy needed to start the reaction.

Enzymes are essentially proteins and will only act in an aqueous environment. An enzyme is specific for a certain reaction or type of reaction. The way enzymes work is called the ‘Lock and Key’ mechanism. The enzyme acts as the lock and the substrate acts as the key. The two fit together in the active site of an enzyme, and are said to be complimentary. The substrate and enzyme, when combined together is called an enzyme substrate complex.

There are two types of enzymes: -
Builder enzymes- These speed up chemical reactions or small chemicals, which have been joint together to make larger ones. Breaker enzymes: - These speed up chemical reactions breaking down molecules into smaller ones. An example of a breaker enzyme is Catalase. Enzymes have certain conditions in which they work best. They have to be in conditions of a certain temperature and pH or can denature or deactivate. If they are at too high a temperature the enzyme is denatured and destroyed. If kept at too low a temperature the enzyme is deactivated but not destroyed.

Catalase is complementary to hydrogen peroxide and breaks it down into water and oxygen. The enzyme Catalase is found in the body in a number of organs and tissues. This includes the liver where the job of the enzyme is to decompose hydrogen peroxide into oxygen and water. It is necessary for the Catalase to break down the hydrogen peroxide as the hydrogen peroxide is a by product of metabolism and is toxic. catalase

Hydrogen Peroxide Water + Oxygen

2H2O2 2H2O + O2

The diagram above illustrates the Lock and Key mechanism. The substrate has a specific shape to fit into the active site of the enzyme. As both the enzyme and the substrate are moving they only lock into place when the two molecules collide.

The diagram above shows the substrate locked in the enzymes active site and then being broken down into the two desired products of water and oxygen. The enzyme remains chemically unchanged and is ready to combine with another substrate molecule.

Possible Variables.

There are three different types of variables. They are : -

Dependant Variables- These are the ones which change automatically due to the experiment. They depend on the experiment and we measure these ourselves. E.g- Amount of water and oxygen produced.

Independent variables- These are the variables we alter ourselves. E.g Concentration of the solution.
Fixed Variables- These Variables remain constant throughout the whole experiment. E.g Time, size, temperature and volume of solution

It is important to have fixed variables so we can determine what factors effect the rate of reaction. E.g If we had the same amount of catalase and kept that as the fixed variable and reacted it with different concentrations of the substrate, and very thing else kept constant, we could determine that the factor affecting the rate of reaction would be the concentration of substrate.

In our experiment we will only have a single independent variable, the rest shall remain fixed and allow us to measure the dependent variable.

There are four possible variables that can enable us to investigate the rate of enzyme activity. They are: - • Concentration of hydrogen peroxide (substrate)
The surface area of the...
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