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The Effect Of pH On Invertase Activity.

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The Effect Of pH On Invertase Activity Introduction Invertase Sucrose+water glucose + fructose Invertase is an enzyme which is usually found in plants. It acts as a catalyst for the hydrolysis of sucrose. (Campbell&Reece,2002) Sucrose is a disaccharide composed of glucose and fructose linked by a glycosidic bond. When this bond is cleaved in a hydrolysis reaction, an equal amount of glucose and fructose. Invertase is a significant enzyme because glucose is an important product of photosynthesis. Invertase is also used in the confectionery industry where fructose is preferred over sucrose because it is sweeter and does not crystallize easily. The reaction is shown as follow: Enzymes are affected by changes in pH. (Campbell & Reece, 2002) Extreme pH values generally result in loss of activity for most enzymes. Furthermore, there is a most favorable pH for enzyme - the point where the enzyme is most active. ...read more.


The 5 test tubes were gently shaken. Then, they were put into a water bath at 37 degrees Celsius for 5 minutes. One drop of 1 drop/ mole Benedict solution was added to each of these 5 test tubes after the 5 minutes incubation. The 5 test tubes were then shaken gently. Finally, the test tubes were put into a water bath at 85 degrees Celsius for another 5 minutes. Observe and record the colour change for each of the 5 buffer solutions containing invertase, sucrose and Benedict solution. Result Invertase's activity differs when placed in solutions of different pH level. Invertase is active at pH 4. It lost its activity at pH of 2, 7, 9, 11. This is shown as the solution with pH of 4 changed its colour from blue to red.(Table 1) In contrast, the solutions with pH of 2, 7 , 9, 11 did not change its colour and stayed blue.(Table 1) ...read more.


This suggests that different enzyme have different optimal pH values. This is significant, because the optimal pH of an enzyme specifies where the enzyme will be active in organisms. For example, pepsin is a specific enzyme found in the gastric juice in stomach. Gastric juice has a pH of about 2 and pepsin functions the best under pH of 2 to hydrolyze protein. By this experiment, the optimal pH can only be approximated to 4.We cannot measure the exact range of pH where invertase is active. Therefore, in this experiment, we do not know the optimum is broad or narrow. Also, we cannot know whether a small pH change would have a large effect or small effect. However, we could repeat the experiment and investigate the effect of pH on invertase by replacing the original solution with a narrower range of pH solution. (Between the pH range of 2~7.) In the end of this experiment we may find the exact pH range where invertase functions the best. ...read more.

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This report of an investigation into the effect of pH on invertase activity adequately describes the method carried out and briefly discusses the results obtained. However, to obtain the higher grades at GCSE, the report needs to follow the tried and tested science investigation structure with sections on hypothesis, control variables, risk assessment and evaluation, all of which were missing here. In particular, practical science must start with a hypothesis, i.e. something to test, which is based on observations and prior knowledge. Similarly, an evaluation of the data collected is vital in order to assess the validity of the data, i.e. its worth so that other scientists can accept or reject the writer's findings.

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Marked by teacher Ross Robertson 10/05/2013

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