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Topics: Chemical reaction, Reaction rate, PH Pages: 13 (3172 words) Published: May 26, 2013

Ashley Njeru

Mrs. Booth

Tuesday, March 19th 2013



The cellular activity of all organisms is controlled through the use of enzymes. An enzyme is a special type of biological molecule, usually a protein, which speeds up a chemical reaction; most are soluble in water or a dilute salt solution. There are about 4000 different enzymes in a typical living cell. If even one of these enzymes is missing or defective, the results can disastrous. Enzymes have a unique three dimensional shape, and this shape determines which reaction it catalyzes. Another term that is used to describe an enzyme is catalyst. A catalyst is a substance that speeds up a reaction, without being consumed by the reaction. (5, 2) Characteristics of enzymes: The shape of the globular protein determines the function, they stress chemical bonds, and they lower the activation energy barrier (EA). This energy barrier must be overcome in order for the chemical reaction to move forward. The enzyme has surface depressions on them called active sites representing the location for catalysis. A substrate (reactant molecule on which the enzyme acts) must fit into the active site perfectly. The enzyme stresses the chemical bond and therefore lowers the activation need to break a bond. (1)

There are many factors that can alter enzyme activity, the most common being temperature and pH level. When temperature levels begin to increase, the rate of the reaction increases as well because the increased kinetic motion in the molecules begins to get stronger and stronger. However, this can only go so far. Once the temperature reaches a certain peak, the kinetic motion begins to denature an enzyme and eventually the enzyme will lose its ability to function.

Enzymes require very specific conditions for them to work appropriately. Typically, each enzyme has an optimal pH level where it operates at its highest efficiency. The rate of the catalyzed reaction will decrease when the pH level either increases or decreases away from its optimal value.(1) The rate of reactions of the enzymes can be further determined with the help of hydrogen peroxide. By placing various hydrogen peroxide solutions with different pH levels in the catalase, this aids in determining the action of catalse to a non-protein catalyst. (6)


The following experiment was to compare the action of catalase to a non-protein catalyst under different conditions.


|3% hydrogen peroxide |Sand | |Manganese dioxide |Mortar and pestle | |Liver |Hot plate | |Potato |600mL beaker | |Ice |Test tubes | |Acidic acid |Scalpel | |4.0 M NaOH | |


PART A: Effect on temperature.

Place a small piece of liver in a test tube and heat until sections C-F are complete in a boiling water bath. Add 2mL of hydrogen peroxide and record your results.

Place a small piece of liver into each of the 2 test tubes. Place one test tube in a 37oC water bath until sections C-F are completed and the second test tube in ice-water until sections C-F are...
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