An Investigation into the Effect of Temperature on the Activity of the Enzyme Catalase.

An Investigation into the Effect of Temperature on the Activity of the Enzyme Catalase

By Christine Mitchell

Introduction:

The catalase is added to hydrogen peroxide (H²0²), a vigorous reaction occurs and oxygen gas is evolved. This experiment investigates the effect of temperature on the rate at which the enzyme works by measuring the amount of oxygen evolved over a period of time.

The experiment was carried out varying the temperature and recording the results. It was then repeated but we removed the catalase (potato) and added Lead Nitrate in its place, we again tested this experiment at two different temperatures and recorded the results.

Once all the experiments were calculated, comparisons against two other groups were recorded. With this information we were able to identify any patterns and similarities.

Hypothesis:

The higher the temperature of water, potato and H²O², the rate at which the Enzyme will work will be faster therefore producing more oxygen.

The reaction will be the same without the catalase (potato). Therefore in both experiments the Enzyme will work more rapidly and produce more oxygen.

Aim:

To test the hypothesis.

Method:

Equipment needed:

The skin of the potato was removed using a scalpel and then cut into 1cm², using a ruler to measure the size of each cube, four cubes are required for each experiment, and therefore at least 36 cubes are required for the full experiment to take place. Fill a beaker half way with water, and place a thermometer in the water. Allow the thermometer to warm to room temperature to gather an accurate reading, and measure the temperature, using the thermometer. A measuring cylinder was used to put 10ml of Hydrogen Peroxide Solution into a test tube, and then four potato cubes were placed into the test tube. The mouth of the test tube was plugged with a delivery tube; the other end of the delivery tube was placed in another test tube that was filled with water. The stop-clock was set for one minute. The test tube that’s filled with water was observed, the number of oxygen bubbles that are released in one minute were counted. Calculations were noted before moving onto the next experiment. Each new experiment that is taken place, ensure a new test tubes, new potato, fresh new H²O² solution and fresh new water is used. A Bunsen Burner was lit with matches; the beaker of water was placed on top of the gauze, which was on top of the tri-pod, above the Bunsen burner, heat the water, the thermometer was placed in the beaker. The temperature was noted for each experiment. The experiment continued with the water at different temperatures e.g. 25°, 35°, 45°, 50° and 60°. The results were recorded indicating the number of oxygen bubbles released at each different temperature.

The experiment was repeated at two different temperatures e.g. 20° and 32°, following the above guidelines, a pipette was used to add five drops of Lead Nitrate to the mixture. Both results were recorded.

The experiment was repeated again, at two different temperatures e.g. 20° and 32°, following the above guidelines, removing the potato (enzyme – catalase), and adding five drops of Lead Nitrate. Both results were recorded.

Results:

The following table indicates the results and calculations of our experiments. (Table 1).

Table 1:

This experiment was noted from three different ...

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Results:

The following table indicates the results and calculations of our experiments. (Table 1).

Table 1:

This experiment was noted from three different groups and a comparison was made. As noted in the table below. (Table 2).

Table 2

By looking at the graph (see Diagram 1, attached), you will see that different temperatures were used, as well as different volumes of potato (enzyme – catalase) and H²O². This gave a completely varied result, but indicated that the higher the temperature, the higher the amount of oxygen bubbles were released. It also indicated that the more potato (enzyme – catalase) that was used, the faster the reaction.

Table 3

The above table (Table3) demonstrates the different reactions that occurred when the experiment was repeated with Lead Nitrate, and then again with Lead Nitrate but without the potato. Each column represents the findings of the three groups; the first group is our own results.

Conclusion:

This would conclude that my hypothesis for the first experiment (potato, hydrogen peroxide) was supported by the experiment. This was indicated by the number of oxygen bubbles that were released. Showing that at the temperature of 50° eighty-four bubbles were released, proving that the higher the temperature the faster the reaction of the catalase.

However, my conclusion on the experiment where the potato was removed and lead nitrate added, it clearly showed that there was no reaction at all. This was demonstrated by my results as well as the two comparisons I made.

Analysis and Discussion:

Enzymes are globular proteins, which are polymers of amino acids. They range in size from 1 x 104 to 1 x 106 daltons with the majority being in the 105 range. Some enzymes have extra molecules other than amino acids, which assist in the reaction they carry out. The protein portion of an enzyme is called the apoenzyme. The non-protein part of an enzyme is called a cofactor. Cofactors can be loosely bound; coenzymes are tightly bound, into prosthetic groups. The complete enzyme (apoprotein + cofactor) is called the holoenzyme.

Enzymes are proteins that catalyze (speed up) chemical reactions. Enzymes increase reaction rates by a factor of about 1 million (ref: Marieb, Elaine N). They do this by lowering the activation energy needed to get a reaction to go forward. All enzymes are specific to single chemical reactions or a small group of related reactions. Each specific enzyme determines which reaction will occur and be speeded up, this means that unwanted chemicals or reactions are reduced.

The results of my experiment indicate that at the temperature of 35° the reaction was the slowest with only twenty-seven oxygen bubbles being released; whereas at the temperature of 50° the reaction was the highest at eighty-four oxygen bubbles being released. This indicated that the higher the temperature the faster the reaction. This experiment was carried out various times by different groups, and it indicated that the amount of catalase (potato) was a significant factor on how slow or quick the reaction, the more potato the quicker the reaction.

The results could vary very much, depending on the amount of potato and H²O² that was used; this is proving in my comparisons’. Showing that the group that used the least amount of potato (1 x 1cm²) and the least amount of H²O² (5cm³) got the lowest reaction. Improvement could be made by ensuring that every experiment that is carried out uses the exact amount of H²O² and the same amount of potato. This would clearly give a more accurate reading.

I would suggest that in future experiments 4 x 1cm² of potato, 10ml of H²O², and temperatures at 20°, 30°, 40°, 50° and 60° are tested. Therefore all results would be more accurate and a better comparison could be made.

Additional Information:

Catalase is one of the most potent catalysts known. The reactions it catalyses are crucial to life. Catalase catalyses conversion of Hydrogen Peroxide; a powerful and potentially harmful oxidizing agent to water and molecular oxygen. Catalase also uses Hydrogen Peroxide to oxidise toxins including Phenols, Formic Acid, Formaldehyde and Alcohols.

Catalase like all enzymes has an optimum temperature and pH at which it works best. This may differ according to the source of the catalase - catalase from liver could have a higher optimum temperature than catalase from potato. Experiments can be done to find out the optimum for your catalase. The pH optimum of potato catalase is pH 7.6.

The pH is the measure of the acidity or alkalinity of a solution. An acidic solution has many hydrogen ions (H+) and a pH below 7. An alkaline, or basic, solution has very few hydrogen ions and a pH above 7. A neutral solution has a pH of 7.

An enzyme that is found in the cells of many living tissues is catalase it speeds up a reaction which breaks down hydrogen peroxide, a toxic chemical, into 2 harmless substances - water and oxygen. The reaction is as follows:

2H2O2 ----> 2H2O + O2

This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a result of many normal cellular reactions. If the cells don’t break down the hydrogen peroxide, then they would be poisonous and die.

There are three essential steps in the participation of the mechanism of enzyme action:

1. The enzyme must attach itself to the substance(s) on which it works. These substances are called the substrates of the enzyme. Substrates attach to a particular part of the enzyme’s surface; this is called the active site. This is very much like a jigsaw puzzle, and particular substrates attach and fit into the enzymes. This is called enzyme recognition.

2. Internal rearrangement of the enzyme substrate forms the product.

3. The enzyme releases the product, showing the catalytic role of the enzyme.

The process then continues again and again with the “free” enzyme to locate its matching substrate(s). Enzymes can be found in every organ of the body. For example, they can change , , and into substances the body can digest. Blood clotting is an example of enzymes at work. Enzymes exist in the mouth (saliva), stomach (gastric juice), and intestines (pancreatic juice, intestinal juice, and intestinal ).

I believe the results I obtained showed precisely the higher the temperature the quicker the reaction, but when the catalase is removed no reaction occurs.

Reference: