The Effect of Enzyme Concentration on Rate of Reaction

Topics: PH, Oxygen, Buffer solution Pages: 9 (2632 words) Published: January 16, 2009

The experiment was carried out to investigate the effects of the increase in the enzyme concentration on the rate of reaction. By using self investigative and experimental skills, the experiment was done in order to determine how the rate of reaction will be altered, whether it will increase, decrease or remain constant when the different concentration of enzymes added.


Enzymes are produced naturally in plant, animal, and microbial cell. There are thousands of different enzyme can be found in any cell. Enzymes can be describe as molecules that are greatly increase the rate of chemical reaction without themselves being changed at the end of the reaction. A chemical reaction involves the conversion of a substrate into a product. This reaction is normally known as an enzyme-catalyzed reaction. In this reaction, the substrate will bind to the active site of the enzyme. Once it is bind, an enzyme-substrate complex is formed. At this form, the substrate is converted into product. Finally, the product will be released.

There are four factors that affect the enzyme activity that is temperature, pH, substrate concentration and enzyme concentration. As for temperature, it will affect the enzyme activity when there is a rise in temperature. When temperature increases, this will automatically increase the kinetic energy. This will then results in the increase of the rate of collision between the enzyme and substrate, but this effect is limited. The rate of reaction will increase up to a certain temperature. At this temperature, the enzyme activity is the greatest. Changes in pH will results in disruption of hydrogen bond of the protein chain. Hence, this will results in changes in shape of the enzymes' active site that then will reduce the effectiveness of the enzyme and the rate of reaction.

Using different type of substrate concentration will also affect the rate of reaction. Increase in substrate concentration will increase the rate of reaction up to a point where all of the active site of the enzymes is occupied. The fourth factor is the enzyme concentration which is the factor that has been investigated in this experiment. When using different concentration of enzyme, the rate of reaction will also change. Any increase in the concentration of enzyme will also increase the rate of reaction up to a point where all substrate are occupied. Substrate concentration will become the limiting factor of the experiment.

In this experiment, the enzyme used is catalase. Catalase is an enzyme normally found in many plant and animal tissues. Generally, catalase break down toxic substances and specifically, it catalyze the decomposition of hydrogen peroxide to oxygen and water as stated clearer in the equation below:

2 H2O2 ↧ 2 H2O + O2

Catalase is the fastest known enzyme. It has one of the highest turnover numbers of all enzymes. A molecule of enzyme can convert millions of molecules of hydrogen peroxide to water and oxygen per second where a normal enzyme would catalyze thousands of molecules per minutes rather than millions. Catalase consists of four polypeptide chains with each over 500 amino acids long. It also contains four porphyrin heme (iron) which act as the enzyme cofactor that will allow the enzyme to react with the hydrogen peroxide. Approximately, the optimum pH value for enzyme catalase is 7, while its optimum temperature depends on the sources of the enzyme but it works at an optimum temperature of 37°C, which is approximately the temperature of human body. Besides, catalase also can break down other toxic substances such as alcohol, formic acid and phenols. Catalase has its inhibitor that is copper (II) sulphate, a heavy metal ion and cyanide poison. Therefore, such enzymes' inhibitor is avoided while conducting the experiment.

Hydrogen peroxide is the substrate in this experiment. This substance is the one who will react with...
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