Amylase Investigation

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An investigation of the relationship between different concentrations of Sodium Chloride and the rate of reaction of Amylase

Marjolijn Hoogevoorst

Yeshvanth Prabakar


Word count: 2222 words


Enzymes are biological catalysts that speed up reactions by lowering the activation energy. Amylase is a type of digestive enzyme found in the pancreases and saliva of humans. Amylase breaks down starch into sugar, allowing large molecules to be digested easily. To function efficiently, amylase requires certain conditions. The effect of different sodium chloride concentrations in this on the rate of reaction of amylase will be investigated in this experiment along with the use of starch and iodine.
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Similarly, a slower decrease in absorbance corresponds to a low rate of reaction. Through altering the various concentrations of NaCl that Amylase is exposed to, the effect of different NaCl concentrations on rate of reaction of amylase can be determined.

Research Question:

What are the effects of different sodium chloride concentrations on the rate of reaction of amylase, measured the spectrophotometry.


Sodium chloride, temperature, pH levels are all conditions that affect the activity of an enzyme. These conditions may denature the enzyme, decreasing its rate of reaction. A conformational change to the activity site of an enzyme will cause the activity of the enzyme to decline significantly. This is because substrate a change in the conformational of the active site of an enzyme prevents the substrate from binding to the enzyme. Sodium chloride affects the charged interactions interactions between the amino acids of the enzyme, deteriorating the active site of the enzyme. However, the enzyme will only deteriorate if there is a high concentration of sodium chloride and not if S3odium chloride is simply present. Therefore, by increasing the sodium chloride concentrations it is expected that the rate of change in absorbance, and therefore rate of reaction of amylase, will decrease exponentially as illustrated in the graph
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This is because high sodium chloride concentrations denature the enzyme, preventing the substrate from binding; as a result the enzyme cannot break down starch into glucose.


Independent: Concentration of sodium chloride (%)

Dependent: Rate of change of absorbance (Abss-1)


-Iodine and starch concentration. Both the concentrations of starch and iodine affect the rate of absorbance. Therefore this will be kept constant by creating the same mixtures, which will be used for all the trials.
-Volume of solution inside cuvette will be kept constant for all trials by adding only 2.5cm3 of starch and iodine solution and 0.5cm3 of Amylase and Sodium-Chloride solution to the cuvette.
-Conducting all trials for the experiment at room temperature 22ºC controls temperature.
-pH is kept at a constant by using the same solutions of Starch-iodine and Amylase-Sodium chloride for all trials.


•Digital weighing scale (0.001g uncertainty) x1
•Volumetric flask 100cm3 (0.1cm3uncertainty)
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