The Effect of Low pH on Enzymes

Enzymes


Enzymes are biological catalysts that are protein-based (Adams, 1996). They quicken bodily reflexes that are necessary for survival. In a day, an organism goes through numerous chemical processes. Each enzyme functions most effectively in a certain set of circumstances ("pH and Temperature Dependence of Enzymes," 2017). Temperature, salinity, and acidity all have an impact on these circumstances. The enzyme can change these conditions to speed up, slow down, or even stop a reaction.

The Experiment


The experiment will make advantage of the catalase enzyme. Animal, plant, and aerobic bacterial cells all have catalase. In the absence of catalysts, Hydrogen Peroxide is a moderately stable compound ("pH and Temperature Dependence of Enzymes," 2017). It decomposes slowly while producing oxygen and water. Various chemical elements can modify the rate of this decomposition. The enzyme catalase works as a catalyst for this reaction. It speeds up the breaking down of hydrogen peroxide to water and oxygen.


2 H202 catalase 2H20 + 02

Experiment Question


What is the effect of lowering the pH of an enzyme in a catalytic reaction? This test will determine the effect of a lower pH level on enzymes.

Hypothesis


A lower pH can be caused by increasing the acidity of cells in which enzyme controlled reactions take place. An enzyme becomes weak if its pH conditions are not met.

Materials and Methods


As I had mentioned earlier enzymes speed up the breaking down of hydrogen peroxide into water and oxygen (REED, 1975). With the production of oxygen gas, the experimental reaction will thus produce bubbles. The height of the bubbles created after a certain amount of time can be used to determine the reaction rate.


The independent variable in this experiment is the level of pH of the catalase solution. This variable is determined by the water and amount of HCL acid used. The dependent variable in the experiment is some bubbles produced. Time is also an independent variable. The time taken to assess the reaction affects the outcome of the experiment. The bubbles will determine the rate of the reaction. Where many bubbles are produced the reaction is first.

Materials


Materials include: Hydrogen Peroxide (1% H2O2 solution), Catalase (well-blended/strained potato extract), HCL acid buffer solutions (pH 7, 5, 2), Water, ten mL Syringes, Test tubes, 10 ml graduated cylinders, Gloves & Goggles.

Procedure


The first step was to select 4 test tubes. In 3 test tubes, I added the enzyme catalase up to the 10mm mark. The fourth test tube was a control experiment, and thus I did not add any catalase.

Test tube 1


In the first test tube, I added 20mm of water. I then adjusted the pH of the water to 2 by adding HCL acid. I then added 40mm of Hydrogen peroxide into the solution and waited for one minute to elapse. After it had passed, I shook the content in the tube for twenty seconds and measured the height of the bubbles produced. I then recorded my findings.


Content: 10mm catalase, pH 2, 40mm, Hydrogen Peroxide.

Test tube 2


I proceeded to test tube two. I added a similar amount of water of 20mm. The pH level was adjusted to pH5 by adding HCL acid. After adding HCL acid, I put 4cm of hydrogen peroxide into the solution. I waited for another minute to elapse before I shook and swirled the content for twenty seconds. The height of the bubble column in the experiment was measured and recorded.


Content: 10mm catalase, pH 2, 40mm Hydrogen Peroxide

Test tube 3


In test tube three, I added the same amount of water (20mm) and no HCL acid. After that, I added 4mm of Hydrogen Peroxide and waited for one minute to elapse. I then shook and swirled the test tube for 20 seconds before I measured and recorded the height level of the bubbles produced in the reaction.


Content: 10mm catalase, pH 7, 40mm Hydrogen Peroxide

Test Tube 4: Control experiment


In the final test tube i.e. test tube four without any catalase enzyme, I added 20mm of water and maintained a pH level of 7. I added 40 mm of Hydrogen Peroxide and waited one minute for the solution to settle. I then shook the content for 20 seconds before I measured and recorded the height of the bubbles that were formed.


Content: pH 7, 40mm Hydrogen Peroxide

Findings


In test tube one I recorded a height of 2mm for the bubbles formed. In test tube 2, I recorded a height of 4mm. Test tube three had the biggest height for the length of the bubbles created. It had a height of 25mm. Test tube four had a height of 1.5mm.


Acidity harbors the effects of enzymes in catalytic reactions. As was expected when the pH level was lowered, the strength of catalysts was weakened. Increasing the pH towards a neutral level increased the strength of enzymes. The experiment was a success. The reaction process and time can be evaluated by measuring the level of gases produced and time taken.

Conclusion


My experiment would have improved if it also tested the effects of a higher pH on enzymes. Testing acidic effects is not enough to establish the effect of altering the pH on an enzyme. The experiment should also test enzymes that have another optimum level rather than a pH of 7 alone. Pepsin breaks down proteins in the stomach at a pH of around 2 in the stomach (Staley, 1940).


Catalase works best at a pH of 7. When the acidity level increases, some bubbles produced decreases. This shows that catalase and other enzyme become weaker as the pH level decreases.


In the test tube without the enzyme (test tube four) the reaction was slower than that with enzymes. Hydrogen peroxide broke down to release oxygen and water at a slower rate. It was slower compared to a reaction which had catalase and an acid. Lowering the pH of an enzyme makes it inactive as it cannot speed up chemical reactions. Each enzyme has its optimum pH.


References

Adams, M. W. (1996). Enzymes and proteins from hyperthermophilic microorganisms. San Diego: Academic Press.

pH and Temperature Dependence of Enzymes. (2017). Enzyme Kinetics, 145-152. doi:10.1002/9783527806461.ch6

REED, G. (1975). Effect of Temperature and pH. Enzymes in Food Processing, 31-42. doi:10.1016/b978-0-12-584852-7.50010-5

Staley, K. E. (1940). Effect of environmental factors on oxidizing enzymes of rose mallow seeds. Lancaster, Pa.

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