Period5.F

Tony Gao, Kate Brush, and Tim Moberg Mrs.Odierna 3/29/10
 * Enzymatic Activity Lab**

Manganese dioxide produces oxygen filled bubbles when mixed with a piece of liver in the glowing splint experiment due to a catalyst in the liver called catalase breaking down the Manganese dioxide and producing oxygen. The same goes for when hydrogen peroxide is mixed with a piece of liver; it will produce bubbles filled with gas due to the catalyst breaking down the hydrogen peroxide. The amount of gas that is released can be recorded by a gas pressure sensor. Catalase, present in the peroxisomes of nearly all aerobic cells, serves to protect the cell from the toxic effects of hydrogen peroxide, which  can attack the delicate sulfur atoms and metal ions in proteins,  by catalyzing its decomposition into molecular oxygen and water without the production of  free radicals. Catalase is an antioxidant, fighting the dangers of aerobic life. The reaction is as follows:  2 H2O2 -- 2 H20 + O2 Without catalase, free iron ions in the cell would occasionally convert hydrogen peroxide into hydroxyl radicals, which can attack and mutate DNA. One theory is that this type of oxidative damage accumulates over the years of our life, causing us to age.
 * Introduction:**

The purpose of this lab is to discover what effect grinding the liver before it is mixed with the hydrogen peroxide, as opposed to just mixing the two without grinding, will have on the gas pressure produced by the reaction. By examining the gas pressure after all the reactions take place we can conclude whether or not the grinding had any affect on the catalase in the liver.
 * Purpose:**


 * Materials**:
 * 125mL erlynmeyer flask
 * cow calf liver
 * gas pressure sensor and usb computer hookup apparatus
 * mortar and pestle
 * Hydrogen peroxide
 * scissors/scalpel
 * 10mL graduated cylinder


 * Procedure:**
 * 1) Cut 1 cm 3 of the liver with the scissors/scalpel and place inside the 125mL erlynmeyer flask.
 * 2) Place the stopper with a valve of the gas pressure sensor on the top of the flask, sealing it.
 * 3) Make sure the software is setup and recording pressure.
 * 4) Open the valve, Measure with a graduated cylinder and Pour 10mL of H2O2 into it, immediately close it, record pressure for any amount of time, but make sure during comparing that the same times are being compared
 * 5) Repeat with a clean flask 1 time.
 * 6) After the 2nd trial, repeat steps 1-5 with these added procedures(put after step 1):
 * 7) Put the cut liver piece into the mortar.
 * 8) Using the pestle, grind the liver for 30 seconds.

Will hand in data table
 * Data:**

Legend: Run 1 and 2 are controls Run 3 and 4 are the ground liver


 * ** Independent Variable ** || Ground/Not ground

||
 * ** Dependent Variable(s) ** || Amount of oxygen(bubbles) created

||
 * ** Controlled Variables **

|| amount of liver, amount of hydrogen peroxide, PH, oxygen bubble size, grinding time, time of reaction

|| || Using a mortar and pestle, the liver will be ground || || Graduated cylinder. PH will be constant assuming a constant amount of hydrogen peroxide and liver is kept. Time of reaction will not be specifically controlled but the same points on the graph should be compared, not different times. ||
 * ** How will you change your independent variable? (be specific) **
 * ** How will you measure your dependent variable? ** || Using the gas pressure sensor, the amount of oxygen gas that the reaction creates can be measured ||
 * ** How will you set up a control? **
 * ** Hypothesis: **

|| If the liver is ground, then the amount of oxygen released by the hydrogen peroxide-catalase reaction will be more than if the liver is not ground. ||

If the liver is ground, then the rate at which the catalase breaks down hydrogen peroxide to form O2 will be higher than if the liver is not ground.
 * Hypothesis:**

b) To make sure that the temperature of the catalase never went above a certain temperature one would first need a thermometer. Next, one would need an ice bath for cooling down the substance or ice to put in if the catalase is in a liquid. One would also need a hot plate or warm water if the substance gets too cold.
 * Analysis Questions**
 * 1) The results show that grinding the liver did not affect the catalase activity. This can be seen by the fact that the rate at which one reaction with liver that had not been ground was much faster than the other reaction with original liver. Also, the rate of one reaction with grounded liver was very close to the first reaction with the original liver.
 * 2) One source of error could be that we did not close the cap fast enough after pouring in the H2O2. This would affect the data by influencing the rate at which the reaction occurs. Also, we may not have completely grounded both pieces of liver. This will affect the results showing if grinding the liver has any affect. One change that could have been made to the procedure would be to grind the liver for at least a minute to ensure that it is fully ground. Also, to use a funnel small enough to poor the H2O2 into the container without having to remove the cork. This would take away the first source of error of unnecessary air entering the reaction.
 * 3) It can be concluded that the peroxisome is the part of the cell that helps to secrete the enzyme. This is a logical belief because it is the area that holds that catalase, the catalase catalyzes the reaction; this is the job of an enzyme.
 * 4) When a person takes ecstasy at a party they are, essentially, inhibiting a part of the cell that participates in metabolic activities. This would lead to a failure of completely digesting substances that enter the body. One risk would be hyperthermia which is an overheating of the body. Since the digestive system no longer has the peroxisomes participating in metabolism due to the intake of ecstasy, the body needs to work harder to complete the metabolic process, thus using more energy and exerting more heat. Hyperthermia can lead to failure of the kidney, liver, and cardiovascular system. This can be exacerbated by the crowded rave environment of a party.
 * 5) a) As a cheese maker, one would want to ensure that their factory is at a moderate temperature; one that is considered “room temperature” to create a favorable environment. If the factory is too hot, the enzymes will die and if it is too cold they will not work properly. Maintaining a constant temperature is an ideal condition to have as well. Also, a cheese maker would want to ensure that the pH level of the catalase is 7.0. The catalase will become inactive at a high of low pH.

Because of stated inaccuracies in the data of this experiment, analysis of this data will be done with the control/ground trial which had the highest rate of oxygen production(run 1 and run 4 respectively).
 * Conclusion:**

Our hypothesis was incorrect, grinding the liver did not have any effect on the rate of the reaction, or the end result(how much oxygen was produced). The reasoning behind the hypothesis was that grinding the liver would increase the surface area which the hydrogen peroxide could contact, however, although grinding in theory would increase the surface area of the liver, it did not, because of the sources of error. The average kPa/sec of the controls was .6519, and the average kPa/sec of the grinded test was 0.7714. There were many sources of error in this experiment. First of all, the equipment used, the erlynmeyer flask and gas pressure sensor, were inadequate for the experiment, and could not measure the full amount of pressure that the reaction created, this caused error in the final data as a linear regression had to be done to average the data, which is not as accurate as if the pressure was measured to the maximum amount of oxygen released by the reaction. The most apparent flaw in the data set was that one trial of the control was significantly lower than the other trial(by about .45kPa/sec), although it is not possible to be certain that this is inaccurate, it is very likely, because two trials of the same test under the same circumstances should result in data sets that are very similar, which this data was not. Secondly, the liver was very sticky, and was very difficult to grind in the mortar. It stuck to the walls of the mortar and easilly turned into a slimy substance which remained on the walls, and otherwise did not grind as well as intended. This could be the reason why the ground and unground data were so similar, because grinding the liver did not make a significant difference in how much surface area it had(but it should have made a difference). Another source of error was that not the same amount of data was polled for each trial, and each trial did not last the same amount of time, which could cause some of the data to become higher or lower than what they should be(because of more/less data averaged to ascertain the slope of the curve). Our method of controlling the time variable, comparing specific points on the graphs, is not possible because of limits of the lab equipment, and the linear regression could not only target a specific timeframe. If we were to do this lab again, if possible, a higher quality set of glassware and gas pressure sensor would be used, and the amount of time that each reaction is allowed to take will be controlled more strictly, so even if more durable equipment is not acquired, a more reliable set of data can be obtained. In conclusion, the end results of this experiment were inconclusive, there were too many sources of error which could not have been controlled given the available materials provided to our group.

Catalase is a common enzyme found in nearly all living organisms which are exposed to oxygen, where it functions to catalyze the decomposition of hydrogen peroxide to water and oxygen. Catalase is a very potent enzyme, one molecule of catalase can convert millions of molecules of hydrogen peroxide to water and oxygen per second.
 * Scientific Concepts Related:**