The Influence of pH on the Activity of Catalase Enzyme Essay


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Enzymes are vitally of import for every life being. because without them the reactions within the cells would happen to decelerate to prolong life. However there are many factors which affect the rate of enzymes reactions. One of them is pH. which influence on the enzyme activity will be the topic of this probe. Catalase of murphy tuber cells will be the enzyme used in the experiment.


What is the influence of different values of pH on the activity of catalase in murphy tuber cells?


Mugwump: murphy phonograph record intervention ( puting them into buffer solutions of different pH values. assorted with hydrogen peroxide ) Dependant: the activity of the catalase. reflected by the rate at which O is evolved. measured at every clip the pH is changed.

Controlled: whether the murphy phonograph record were chemically threaten. whether the catalase and H peroxide concentration was the same in every sample ( whether the murphy phonograph record were accurately cut and whether they all came from the same murphy. whether the same fresh H peroxide was used in all samples ) and whether the temperature remained the same during the whole experiment.


Different pH values act upon the activity of catalase. It was obtained from the literature. that the scope of pH values. at which catalase works is about 4 to 9. with an optimal pH of 7. Bearing this in head the undermentioned hypothesis has been made: If the murphy phonograph record are placed into a trial tubing with H peroxide and a buffer solution at pH about 7. so the activity of catalase will be the greatest. If the pH value is less or more than 7 the activity of the enzyme will be smaller.


An enzyme is a biological accelerator. This means that it’s a substance. produced in life beings. which speeds up a certain reaction. because it lowers the activation energy. Activation energy is the sum of energy. which is needed for the reaction to get down.

Catalase is one of the fastest acting enzymes known. which speeds up the decomposition of H peroxide. emancipating O gas and let go ofing energy as shown below:2H2O2 2H2O + O2Hydrogen peroxide is a toxic byproduct of metamorphosis in certain pant and animate being cells. and in a reaction catalyzed by catalase. it is expeditiously decomposed into harmless substances- H2O and O.

Buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. It has the belongings that the pH of the solution alterations really small when a little sum of acid or base is added to it. Buffer solutions are used as a agency of maintaining pH at a about changeless value in a broad assortment of chemical applications.

A pH is the step of the sourness or alkalinity of a solution ( see figure 1 ) . An acidic solution has many H ions ( H+ ) and a pH below 7. An alkaline. or basic. solution has really few H ions and a pH above 7. A impersonal solution has a pH of 7.

The optimal pH of an enzyme. is the value of pH at which the enzyme has its maximal efficiency.

Figure 1. Increasing alkalinity and sourness on pH graduated table.

In this experiment. murphy phonograph record in solutions of known pH act on H peroxide. and the rate of O evolved is measured. This reflects the activity of the catalase in the murphy.

The indispensable expression for informations analysis were: arithmetic mean: Standard divergence: Standard mistake: wheres is the sample criterion deviationn is the size ( figure of points ) of the sample.


scalpelcork borerpetri dishrulerboiling tubesupport standmanometer tubing with gum elastic spile ( about 2mm diameter ) beaker ( 10ml ) pipetteclipclockpotatohydrogen peroxide ( 50 milliliter ) citric acid phosphate buffersat pH: 3. 4. 5. 6. 7. 8 ( 100 ml each ) tap H2O


Adding H peroxide to the samples should be carried out carefully. as it is caustic and may fire the tegument or vesture.

1. With a cork bore bit a cylinder of murphy tuber tissue of approximately 1cm in diameter and at least 6cm long was cut. The swayer was placed beside the cylinder and it was cut into 60 discs 1mm midst. As the phonograph record were cut. they were instantly placed under H2O in petri dish.

2. For mensurating the rate of O evolved. the technique shown in Fig. 2 was used. First the boiling tubing was placed in a support base and the manometer tubing was filled with H2O ( but merely to a degree. which was marked on the tubing ) . Then the boiling tubing was filled with 5 milliliters of buffer solution at pH 3. Carefully 10 murphy phonograph record were added. Then. 5ml of H peroxide was added to the boiling tubing and it was carefully assorted.

3. Equally shortly as the H peroxide was added. the gum elastic spile was sticked into the boiling tubing and the cartridge holder at the top of the boiling tubing was closed in a manner. that it provided an air-tight seal ( see Fig. 2 ) .

4. As the reaction began and the O was produced the H2O. which was in manometer was pushed down the left manus side of the manometer tubing. Time how long did it take for the fluid to lift through a distance of 5 centimeter in the right manus side of the tubing was measured. The consequence was recorded.

5. Equally shortly as the H2O has reached the pronounced degree in the right manus side. the cartridge holder at the top of the boiling tubing was opened so that the manometer H2O returned to its original place.

6. Points 3-5 of the process were repeated 3 times more and the consequences were recorded. The mean reading was worked out and recorded.

7. After 4 measurings the gum elastic spile was removed and the tubing was washed out.

8. Five farther trials were carried out. each with a fresh set of 10 murphy phonograph record. The same process was followed but with buffer solutions 4. 5. 6. 7 and 8 in bend. At every clip a clean beaker was used to mensurate 5 milliliter of buffer and H peroxide. The information was recorded.

9. The topographic point of work was cleaned up.

10. The information analysis was carried out.

Figure 2. Technique for mensurating the rate of development of O from H peroxide in the presence of life tissue.


The row informations. which was collected during the experiment. is shown in Table 1.

3. Finally it was checked. whether 68 % of clip values are in a scope of standard divergence: e. g. for buffer solution at 3 pH: ten + S = 199. 5 + 7. 43 = 206. 93x- S = 199. 5- 7. 43= 192. 07Three out of four clip values ( 75 % ) are in the scope of standard divergence.

Similar was done with clip values of other buffer solutions. ( see Table 2 ) Table 2. Valuess of mean. standard divergence and standard mistake of times at which O was evolved from buffer solutions from 3 to 8 pH.

Value of pH of buffer solution3 pH4 pH5 pH6 pH7 pH8 pHMean of times ( s ) [ +/- 0. 5 s ] 199. 5165157154. 2559. 2560. 5Standard divergence ( 3sf ) 7. 4313. 027. 7815. 666. 577. 50Standard mistake ( 3sf ) 3. 726. 513. 897. 833. 293. 75Whether 68 % of values are in a scope of SDYes ( 75 % ) No ( 50 % ) No ( 50 % ) Yes ( 75 % ) Yes ( 75 % ) No ( 50 % ) Graph 1. Rate of decomposition of H peroxide catalyzed by catalase at different pH values.

Graph 2. Average values of clip at which O was evolved during decomposition of H peroxide catalyzed by catalase in manometer tubing at different pH values.

CONCLUSION AND EVALUATIONThe informations support the surrogate hypothesis that the value of pH at which catalase works the most expeditiously is about 7 ( see Graph 1. ) . When the pH is lowered from 7 to 3 the efficiency of catalase decreases more than a half. Besides. when the pH is greater than 7 the efficiency of the enzyme begins to diminish. Unfortunately the scope of pH at which the activity was investigated was really narrow. so it can be merely assumed that the informations on the graphs are usually distributed ( because it can be predicted that on the first graph the rate of reaction after 8 pH will go on diminishing. and on the 2nd graph the average value of clip at which O is evolved will go on increasing after 8 pH ) .

Looking at the mistake bars on the 2nd graph it can be concluded the average values of clip at 4 pH and 6 pH have the smallest statistical tantrum to the information. Therefore the most inappropriate measurings of clip at 4 and 6 pH could be excluded from the computations ( see Table 1 ) . Excluding some measurings from computations might be besides done for 5 and 8 pH values. because with these measurings merely 50 % . alternatively of 68 % . of the consequences are in a scope of standard divergence ( see Table 2. ) .

The possible account of the fact. that the informations support the hypothesis. may be: about all known animate beings use catalase about in every organ. peculiarly high concentrations happening in the liver. where the pH is about 7. hence this is besides the value of optimal pH of catalase. When the pH is lowered the catalase’s activity decreases. because the enzyme becomes denaturated – its construction is changed which consequences in the loss ( normally permanent ) of its biological belongingss. At the molecular degree. the third construction of the catalase is altered but the peptide bonds between amino acids are left integral. The denaturation involves the break of covalent interactions between amino acid ironss. non-covalent dipole-dipole interactions between polar amino acerb side ironss and the environing dissolver. and eventually the break of Van der Waals interactions between non polar amino acerb side ironss. The denaturation occurs besides when the pH is greater than 7 and it increases.

Catalase is besides cosmopolitan among workss. in which the optimum pH for the enzyme is similar to the pH in animate beings. That is why it may be concluded that the optimal pH for murphy catalase is 7. It may be misdirecting. because it is a known fact that murphies are grown in dirt of pH about 6. which means it is significantly lower than the optimal pH of catalase. But it was obtained from the literature. that many works cells at the beginning of their being grow in an environment of a lower pH than the optimal pH of their enzymes. That is why it assumed that optimal pH of murphy catalase is about 7. although the murphies turn in a somewhat acidic environment.

The whole experiment could be carried out thanks to utilizing buffer solutions. A buffer solution is one which resists alterations in pH when little measures of an acid or an base are added to it. It was valuable to utilize buffer solutions because thanks to them the pH didn’t alteration. when the H peroxide was added to it.

Although the informations support the hypothesis. some betterments to the experiment can be implemented. First of all. in order to look into. whether the buffer solutions at different pH are made right. before the experiment the United States Public Health Service should be examined with an electrical pH metre. The most accurate clock of all available should be used in order to obtain the most accurate informations. It is important. that the manometer tubing and gum elastic spile are airtight. hence the equipment used should be new and unfailing. Finally it would be good to make more than merely 4 measurings at every pH and besides a wider scope of pH should be investigated. because with more consequences statistics computations would be more precise.

Neglecting these things may be a beginning of inaccuracy in the experiment. But it can besides be caused by other possible experimental mistakes. These are: systematic mistakes: the truth of the clock measurings was merely to the whole seconds. graduated tables on the beakers were minimally differentrandom mistakes: utilizing murphy phonograph record from different murphy species. inaccurate lavation of the tubing before make fulling it with another buffer solution. inaccurate film editing of the phonograph record and the clip of human reaction ( when it comes to get downing and halting the clock ) .

Using the same apparatus the volume of the gas evolved per unit clip can be measured. In order to make it. the graduated table on the manometer tubing should be labeled. Then the experimental clip period should be determined ( for illustration 5 seconds ) . Finally. utilizing the same process as in the experiment described the evolved gas volume should be read on the graduated table as the determined clip of measuring ended.

Catalase can break up besides other substances such as methanal. formic acid. phenols and intoxicants. Using these substances as a substrates for the catalase and the same setup some farther experiments can be carried out. It is besides possible. that utilizing the same setup. the activity of murphy catalase can be look intoing by altering the temperature of the samples. or adding different sums of H peroxide to different samples. or puting in a tubing different Numberss of murphy phonograph record. But it is of import to retrieve that these processs can non be carried out at the same time- merely one option ( variable ) can be changed and at the same clip the others should be controlled and remained unchanged.


stuffs from the biological science classesTaylor. Green. Stout: Biological Science 1. Cambridge University Presshttp: //www. chemguide. co. uk/physical/acidbaseeqia/buffers. htmlhttp: //en. wikipedia. org/wiki/Denaturation_ ( biochemistry ) hypertext transfer protocol: //en. wikipedia. org/wiki/Enzyme_kinetics # Chemical_mechanismhttp: //en. wikipedia. org/wiki/Catalase


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