Investigating the Relationship Between Concentration of Sodium Chloride and the Rate of Reaction of Enzyme Amylase

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Seung Soo (Jason) Lee 002213-065

Internal Assessment – Investigating the Relationship between Concentration of Sodium Chloride and the Rate of Reaction of Enzyme Amylase

Research Question:
How will changing the percentage of sodium chloride concentration affect the rate of reaction of enzyme amylase, measured using the absorbance of starch and iodine with a spectrophotometer.

Introduction:
Amylase is an enzyme that is involved in the human digestive process. Found in both the human pancreas and the human saliva, amylase breaks down starch into sugar so that large molecules can be easily digested1. Like all enzymes, amylase must be kept in a certain condition in order to function properly. In this experiment, the effect of sodium chloride concentration on the rate of reaction of amylase will be investigated with the use of starch and iodine. When starch is mixed with iodine, the coils of beta amylose molecules found in starch trap iodine, causing the mixture to turn into a shade of blue-black. 2 When starch is broken down into glucose, however, the monosaccharide does not react with iodine. Therefore, glucose does not change color even when it’s mixed with iodine. Correspondingly, when drops of amylase are inputted into a blueblack mixture of starch and iodine, the starch molecules will be broken down into glucose molecules, causing the mixture to turn colorless. Thus, the rate of reaction of amylase correlates to the absolute value of the rate of change in absorbance of the solution. A rapid decrease in the absorbance of the blue-black color equates to a high rate of reaction of amylase, whereas a slow decrease in absorbance signifies a low rate of reaction. In this experiment, an external variable of sodium chloride will be manipulated into the amylase enzyme to determine the effect the concentration of sodium chloride on the rate of reaction of amylase. Rate of Reaction = │ │

1

"Amylase." Wikipedia. N.p., n.d. Web. 12 Jan 2011. .
2

Senese, Fred. "How Does Starch Indicate Iodine?." N.p., 15 Feb 2010. Web. 6 Jan 2011. .

Seung Soo (Jason) Lee 002213-065

Hypothesis:
As aforementioned, amylase, like all enzymes, must be kept under a certain set of conditions in order to function properly. Factors such as pH level, temperature, and salt concentration could all denature the enzyme and decrease its activity. . When a substrate can no longer bind to the active site of an enzyme due to its conformational change, the enzyme activity and the rate of reaction of the enzyme drops significantly. For instance, a high concentration of sodium chloride would alter the electrostatic interactions between charged amino acids, causing conformational change in the enzyme and destroying its active site.3 Furthermore, the presence of sodium chloride will only have little impact on the enzyme structure unless the sodium chloride concentration is very high, when it could completely denature the enzyme. Therefore, an enzyme should experience an exponential decrease in its rate of reaction as the concentration of sodium chloride is increased Rate of Reaction of Amylase, Abss-1 Concentration of Sodium Chloride, % Figure 1: Prediction of the Effect of Sodium Chloride Concentration on Rate of Reaction of Amylase Enzyme

Thus, the hypothesis for this experiment is that if the sodium chloride concentration is increased, then the rate of reaction of amylase will decrease. A high concentration of sodium chloride will denature the enzyme amylase and, as a result, it will no longer be able to break down starch into glucose. The figure above demonstrates that the average rate of change in absorbance will undergo an exponential decrease as the concentration of sodium chloride is increased.

3

"Rule of Protein Structure." N.p., n.d. Web. 6 Jan 2011. .

Seung Soo (Jason) Lee 002213-065

Variables:

Variable Independent

Description Concentration of sodium chloride

Units / range %

Method of Measuring / Manipulating...
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