Effect of acidic fluid on enzyme activity

 Effect of acidic fluid on enzyme activity
Each enzyme has a particular optimal pH required for its functioning. Within that pH
value the enzyme performs the chemical reaction at the highest rate. Further increase in pH or
drop in pH results in decrease in the activity of enzyme. As a result, chemical reaction, catalyzed
by the enzyme, is carried out slower.
In the current experiment I wanted to investigate the effect of pH on catalase enzyme. It
is an enzyme that allows the cell to get rid of the excess hydrogen peroxide. It splits hydrogen
peroxide down into oxygen and water molecule. As far as catalase is present within
peroxisomes, its optimal pH should be equal to the pH value of solution inside the peroxisomes.
Peroxisomes have a pH value between 6.9 and 7.1. Thus, the hypothesis was that the highest
rate of enzyme activity would be observed within the neutral pH values while pH values lower
than 7.0 will lead to decrease in the rate of reaction catalyzed by catalase.
First of all, solutions of different pH value were prepared. Hydrochloric acid of different
concentrations was used to create acidic pH. Five flasks were used for the experiment.
Concentration of each of the solutions was measured with the help of litmus papers. pH values
of 3, 4, 5, 6 and 7 were reached. Each of the flasks was labelled according to the pH value of the
solute inside it. It was very important to add the same amount of solute to each flask. The
volume of solute in each flask was 5 cm3.
Then, catalase was isolated from the sample. Catalase is present in the significant
amounts in liver. Thus, about 1 cm cubed in size (unprocessed and uncooked) liver pieces were
used for the experiment. 10 pieces of liver were ground with water (about 20 cm3) and a little
sand. This process led to the breakdown of liver cells. As a result, they released their content
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Sample: Biochemistry - Effect of an Acidic Fluid on Enzyme Activity
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and catalase was within it. The resulting mixture was filtered in order to get rid of the
extracellular material and fibber. The resulting filtrate was equally divided between the test
tubes with solutions of different pH values. 1cm3 of hydrogen peroxide was added to each tube.
Then, a small apparatus was created in order to make the results not just qualitative but
quantitative. Each test tube was closed with a cork containing a thin tube within it. The tube
entered the solution in each tube with its one end and the second end was submerged into a
box filled with water. The tube’s end was present in the graduated test tube present in that
water in the upside down positions. The initial water level within that tube was marked. Thus,
any gas release could be detected and approximate volume of gas released could be measured.
The gas was to move from the solution containing liver extract to the box with water. There, it
had to cause an increase in water level within the upside down placed test tube. That increase
was detected and the volume of gas released was calculated.
Gas production was caused by catalase. It broke down hydrogen peroxide present
within the test tube into water and oxygen. Oxygen was released in the form of bubbles.
Calculation of the amount of bubbles produced per minute could be used as a way of
determining the enzyme activity.
In the result, the following was observed: high-rate bubbling took place in the test tubes
containing the solutes of pH 6.0 and 7.0. Some lower rate of bubbling was observed in the test
tubes with pH value of 5.0. No bubbling at all was present in the test tubes with the pH values
of 4.0 and 3.0. The amount of gas released was also measured. In the case of tube with ph 7.0
the volume of gas released was 0.15cm3. In the case of tube with pH 6.0 the volume of gas
released was 0.1 cm3. In spite of the equal high rate of gas release in tubes with pH 6.0 and 7.0,
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the actual volume was different. Thus, human visual analyzer is not an all-sufficient tool in
research results measurement. The change in volume was not detected in any other tube.
Thus, the highest rate of bubbling and volume of gas released in the test tube containing
the solution of pH 7.0 indicate that catalase works at the highest rate in this tube. A gradual
decrease in both rate of gas production and gas volume is observed in the case of decrease in
pH with respect to 7.0.
Thus, enzyme activity was inhibited by the presence of acid in the solution. In order to
explain the effect of acid on the rate of enzymatic reaction we should remember that enzymes
are proteins. Each protein must maintain its three-dimensional shape in order to perform its
functions properly. Low pH means that hydrogen ions concentration is high. Thus, hydrogen
ions present in the solution may compete with the slightly positive hydrogen atoms of the
protein molecule for the abil