Enzyme Catalyst Lab-Write Up

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The Effect of pH on the Rate of Enzyme Catalysis of Catalase

The objective of this lab was to develop a protocol to investigate the effect of an environmental variable on the catalytic function of an enzyme. More specifically, the objective was to perform an experiment in order to test the effect of pH on the function of the enzyme catalase.

Enzymes are proteins that act as catalysts for reactions. This simply means that enzymes lower the activation energy required for a reaction to take place, allowing a particular reaction to take place much quicker and easier. Specific enzymes only lower the activation energy for specific reactions, and enzymes are shape-specific. The unique folds of the amino acid chains that make up an enzyme result in the formation of a specifically shaped active site. When the reactants of a reactions, called substrates, fit perfectly into the active site of an enzyme, the enzyme is able to catalyze the reaction. The activity of enzymes is affected by both the concentrations of enzymes present and the concentration of substrate present. As the amount of enzyme present increases, the rate of reaction increases. Furthermore, as the amount of substrate increases, the rate of reaction will initially increases. Most enzymes require specific environmental conditions to be met in order for them to function properly and efficiently. These conditions include temperature, then concentration of salt, and the pH level. If the optimum conditions for an enzyme are altered, the enzyme may denature, or change its shape, and deactivate. As a result, the enzyme would no longer to be able to catalyze the reaction, and the reaction rate would significantly decrease ("Worthington Biochemical Corporation").

Catalase is found in all organisms that use oxygen for their metabolism. The enzyme is found in high concentrations in a organelle in cells called the peroxisome. One of the functions of catalase is to prevent a toxic accumulation of hydrogen peroxide (H2O2) in cells. It catalyses the conversion of hydrogen peroxide to water and molecular oxygen. Hydrogen peroxide is a by product of metabolic processes. It is usually produced in peroxisomes when they partially oxidize fatty acids. When catalase is absent, the reaction it catalyzes is spontaneous, but at very low rates that are not able to reduce the harmful effects of hydrogen peroxide (Crook).

Research Question and Hypothesis:
Question: How will altering the pH level of a solution affect the rate of enzyme catalysis of the enzyme catalase?

Hypothesis: If the enzyme catalase is placed in different solutions containing different pH levels, the enzyme will function most effectively at a neutral pH, or a pH of 7. As the pH of the solutions are lowered, catalase will begin to work less effectively, and the rate of reaction will begin to decrease. Catalase, like most enzymes, works best in specific environmental conditions. The reason that catalase will begin to work less effectively is because as the pH decreases, and the environmental conditions are changed, the change in pH will begin to denature and deactivate the enzymes. As more and more enzymes become deactivated, the rate of reaction decreases.

* Hydrogen Peroxide (1% H2O2 solution)
* Catalase (well-blended/strained potato extract)
* Sulfuric Acid
* Buffers (pH of 7, 6, 5, 3)
* Potassium Permanganate
* Water
* 10 mL Syringes
* Plastic Cups
* Beakers
* 10 mL graduated cylinders
* Gloves
* Goggles

1 Before the experiment began, a baseline was determined. 2 Five 50 mL beakers were labelled with the pH of the buffer that was being tested (Control, 6, 5, 3). The pH of the solution was the independent variable. 3 10 mL of 1% hydrogen peroxide solution was added to each beaker. 4 10 mL of the correct buffer solution was added to the first corresponding beaker. 5...
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