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Enzyme Lab

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Enzyme Lab Examination of how the concentration of substrate (H2O2) affects the rate of Enzyme Activity (Liver). Sean Williams Lab Partner: Jaemin Cho IB Biology Standard Level November 18, 2010 Introduction Enzymes are proteins produced by living things that operate as biochemical catalysts (speed up chemical reactions). These enzymes are formed from a sequence of amino acids that take on a specific three-dimensional structure. Along this structure, there is a spot called the active site, where the substrate "matches" the shape of the site. An analogy can be used to explain this in the way that a lock and key are specific and match each other. Here, the lock is the enzyme's active site while the key is the substrate. Substrate is the medium or surface that an organism attaches to. This base or foundation is what the enzyme "works" on. The substrate binds with the enzyme's active site, and the enzyme catalyzes, leading to a chemical reaction. Focused Problem I will investigate how the concentration H2O2 (substrate) will affect the rate of the enzyme-catalyzed reaction (liver). ? This will be observed by placing a disk of liver into a test tube, and adding 5ml of H2O2 into the test tube. The rate of enzyme-catalyzed reaction will be observed by measuring how much water is displaced from the 100ml graduated cylinder, which is filled with water (placed in a water basin). The amount of water displaced is a result of the enzyme-catalyzed reaction. ...read more.


10. Time 2 minutes of the reaction using a stopwatch, and keep an eye on the displacement of water in the graduated cylinder. 11. As 2 minutes is reached, take off the cork from the test tube. The reaction has stopped. 12. Record how much water was displaced from the graduated cylinder. 13. Do this another 4 times for 3% of H2O2. After this set is done, repeat the whole procedure again, but this time changing 3% to 7%(+4% each set). Do each set of results 5 times to get an accurate reading of your results. Setup Raw Data Table 1 - Water Displacement measurements in 100ml Graduated Cylinder from enzyme-catalyzed reaction using different concentrations of substrate (+4%) over a time period of 2 minutes Substrate Concentration /�2 ml 3% 7% 11% 15% 19% Total displacement of water in graduated cylinder /ml � 2ml Trial 1 46 52 58 56 58 Trial 2 44 50 54 62 58 Trial 3 46 52 58 56 62 Trial 4 40 50 62 60 54 Trial 5 46 46 58 58 62 Average 44.4 50 58 58.4 58.8 ==>Table 1 shows our collection of data, in which we recorded the total displacement of water in the graduated cylinder for each trial and concentration of our experiment (5x5). The average of these results is show in the last row. Table 2 - Standard Deviations of Error Bars for Water Displacement measurements in 100ml Graduated Cylinder from enzyme-catalyzed reaction using different concentrations of substrate (+4%) ...read more.


As I am not a robot, some times I was not able to close the test tube off as quickly as other times, leading to an escape of some of the reaction. Obviously we were not able to record this "lost" reaction, therefore some of our results do not reflect the true amount of reaction taken place. Improvements To control the amount of liver used in the experiment, a good way may be to get frozen 1 cubic centimeter cubes of liver. This way, we are certain that one trial has no more liver than another. By being in this frozen state, we are then able to leave it for a few minutes, and it would still be able to use. A 1 cubic centimeter cube would have a definite mass and volume, therefore making results much more accurate and trustworthy. A better method to close the cork over the reaction in the test tube may be to have the cork on over the cubic centimeter of liver from the first place. Another opening at the top of the cork would lead to a syringe, where 5ml of H2O2 is placed. When the H2O2 is injected, we can start timing for our results without losing any of the reaction to the outside air. All the reaction would stay inside of the test tube. By doing this, we can be much more certain that no other "factors" are affecting the rate of reaction other than the concentration of the substrate. ' ...read more.

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