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The Rate of Enzyme Reactions

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Introduction

BIOL 130-017 Room: B2 151 Time: Wed 930AM - 12:20AM Date of Experimentation: 11/04/09 The Rate of Enzyme Reactions Introduction The purpose of this lab was to investigate what factors affect the direction of an enzyme reaction. The variables tested in this experiment were substrate concentration, enzyme concentration and reaction time. Enzymes are important biological catalysts that are required to drive chemical reactions for normal cell function. A catalyst is a substance which promotes chemical change without being consumed in the reaction. (Hasselberger, F.X. 1978) They are also important metabolic mediators, responsible for every reaction in the cell. (Karp, G. 2007) In this experiment two types of enzymes were used to test the variables of the experiment. The enzymes were salivary amylase and phosphorylase. Enzymes are used to accelerate the rates at which a favourable chemical reaction proceeds, however there are factors that affect the effectiveness of the enzyme activity. First, all of the chemical reactions take place at an active site. This is the part of the enzyme molecule that is directly involved with the binding of the substrate. Substrates are reactants bound by an enzyme. (Kuby, S.A. (1991). When the substrate concentration increases, the rate of enzyme activity will increase as well. This is because there are more interactions between the substrate and enzyme molecules. However, gradually a maximum will be reached and at this point the rate of enzyme activity will remain constant. This is when all the available enzyme, is saturated with substrate, has been converted to ES, enzyme substrate complex. (Karp,G. 2007) ...read more.

Middle

Table 6. Initial Iodine Test Test Tube +ve/-ve 1 - 2 - 3 - 4 - 5 + After the iodine test, the following results were obtained. Table 7. Initial Benedict Test Test Tube +ve/-ve Appearance 1 + Opaque, greenish blue, orange precipitate 2 + Translucent bluish green, orange precipitate 3 - Transparent blue 4 - Transparent blue 5 - Transparent blue After the Benedict test, the following results were obtained. Table 8. Test Tube Solutions for Water Bath Test Tube Solutions 6 * 2 ml of 10% salivary amylase solution 7 * 2 ml of 5% salivary amylase solution 8 * 2 ml of 2% salivary amylase solution 9 * 2 ml of 1% salivary amylase solution 10 * 2 ml of water 11 * 2 ml of 1% starch suspension * 2 ml of McIlvaine's buffer 12 * 2 ml of 1% starch suspension * 2 ml of McIlvaine's buffer 13 * 2 ml of 1% starch suspensio * 2 ml of McIlvaine's buffer 14 * 2 ml of 1% starch suspension * 2 ml of McIlvaine's buffer 15 * 2 ml of 1% starch suspension * 2 ml of McIlvaine's buffer The following solutions were added to test tubes #6-15. These test tubes were immersed into a water bath at 37oC for 5 minutes. This is the optimal temperature for salivary amylase activity. Table 9. Test Tube Solutions for Iodine Test Test Tube Mixed with Test Tube Final Solutions 11 6 * 2 ml of 1% starch suspension * 2 ml of McIlvaine's buffer * ...read more.

Conclusion

Graph of concentration of salivary amylase enzyme vs. time, this result is true. The iodine test for test tube 12, which was mixed with #7, reach the end point at 135 seconds. This test tube contained 5% of salivary amylase solution, therefore the rate of enzyme activity was the second fastest compared to the next two concentrations. The iodine test for test tube 13, which was mixed with #8, reached the end point at 270 seconds. This test tube contained 2% of salivary amylase. The iodine test for test tube 14, which was mixed with #9, reach the end point at 480 seconds. This test tube contained 1% of salivary solution. Test tube 15, which was mixed with #10, reached the end point the same time as test tube 13. As one can see, as the concentration of salivary solution decreases, the rate of enzyme activity takes longer. This is because there is less enzymes working on breaking down the maltose off the ends of the starch chains. In conclusion, the results of the lab were as expected. When the concentration of substrate was increased, the rate of enzyme activity also increased accordingly. When the rate of enzyme decreased, the rate of enzyme activity also decreased. A possible source of error is while timing the intervals for iodine testing, human reaction is always delayed. Although the instructions say to test it for example every 5 seconds, the time the iodine test performed might actually be approximately 7-9 seconds. This small delay may cause errors in the results. ...read more.

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