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The effect of an inhibitor on sucrase activity.

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Nang The effect of inhibitor on sucrase activity Introduction Sucrase is an enzyme which catalyses the hydrolysis of sucrose into glucose and fructose. The products of the reaction are reducing sugars (glucose and fructose). Like many enzymes, sucrase is a globular protein and its structure is maintained by hydrogen bonds, disulphide bridges and the ionic bond. Sucrase has a specific site called active-site where substrate molecules (sucrose) bind to form enzyme-substrate complex. The shape of the active-site is so specific that only sucrose can fit in. This is called lock and key mechanism and suggests that one enzyme can only catalyse one reaction. However, enzyme slightly changes its shape when substrate binds to its active- site. This process is known as an induced fit. The presence of these molecules can be tested by using Benedict's solution. The reducing sugar means that it can reduce the copper (II) in Benedict's solution into copper (I) which is red precipitate. In this experiment, we are looking at the effect of inhibitor on sucrase activity. Inhibitor is a substance which slows down the rate of enzyme controlled reaction. Hypothesis The rate of formation of glucose and fructose will slow down with the presence of silver nitrate solution compared with the rate of reaction which does not contain silver nitrate. ...read more.


because (T1) graph is steeper than (T2) graph. This shows that more reducing sugar is being formed from non-inhibited reaction compared with inhibited reaction over the same period of time. The rate of formation of enzyme-substrate complex is higher without the presence of silver nitrate because all the active-sites are available for sucrose molecules to bind and form enzyme-substrate complexes. Enzymes are working at their maximum rate so more and more products are formed as the reaction proceeds. But with the presence of silver nitrate, very few products are formed. This is because silver nitrate binds to sucrase at allosteric sites and causes the change in shape of the enzymes which in turn alter the specific shape of the active-sites. Fewer and fewer active-sites are available for sucrose as the reaction proceeds, resulting in fewer enzyme-substrate complexes. Therefore fewer glucose and fructose are formed. For the reaction in the medium without silver nitrate, we expect the graph to flatten off after a certain period of time. But this reaction cannot give the graph this shape because it needs a longer time for the experiment. At this particular point where the graph flattens off, there can be three possible reasons. * All the substrate molecules are used up during the reaction. The volume of the substrate is constant in the experiment. ...read more.


But we didn't have enough time to repeat the experiment. We also could not get the result until the graph is flatten off which we expect to get. All this could be done if we were allowed a longer time. There was another uncertainty where we had to compare the colour of our result to that of the standard solution. Some of our result did not perfectly match with the standard colour (e.g. the colour lies between 0.22 and 0.17moldm-3) and thus we took the reading between those two readings. This could possibly give us the anomalous points on our graphs. A more accurate reading could be obtained if we used the colorimeter to measure the colour of the solution. This would give us a more reliable result because the colorimeter would be calibrated each time the reading was taken. There was the other way of measuring the concentration of reducing sugar. The precipitate could be filtered out and dried. We could measure the dry mass of the precipitate and work out the concentration of reducing sugar. Other possible coursework This experiment can be adapted to investigate the effect of the following factors on the enzyme activity. 1. The temperature 2. The pH 3. The enzyme concentration 4. The substrate concentration 5. The active-site directed inhibitors ?? ?? ?? ?? 1 ...read more.

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