Important note: This sample lab describes a demonstration completed in class. The demonstration in class may have varied slightly from the presented material below. This is only a sample lab; individual lab reports may require additional specific information or calculations.
Jen LaBombard
Biology II
October 2013
Impacts of hydrogen Peroxide on Liver in Varying Conditions
Introduction: The liver is an amazing organ that has many different functions in the body. The liver can function to filter the blood and protect the body among other things. Within the liver is an enzyme called catalase (Science Buddies, 2012). This enzyme causes a release of oxygen gas when exposed to hydrogen peroxide. A similar reaction can be seen on human skin when hydrogen peroxide is poured over a scrape and bubbles appear on the abrasion. This reaction between an enzyme and a substrate can be impacted by a variety of factors such as changes in pH, temperature, and amount of enzyme present. Without enzymes in the body, many reactions would not be possible because they take too long to complete. Enzymes act as catalysts to increase the speed of reactions. They are so important in the body that some argue they should be supplemented into the daily diet(Freuman, 2013). Weather naturally occurring or through supplementation, tests can be done to show the presence of enzymes by providing the substrate in which it will react.
Problem, hypothesis & variables: What is the impact of changing temperature or surface area on the ability of the enzyme in liver to react with hydrogen peroxide?
If hydrogen peroxide is added to a sample of liver that was exposed to heat or had its surface area changed by grinding, then the enzyme function of the heated piece of liver will be reduced as measured by fewer oxygen gas bubbles produced because enzymes are sensitive to changes in temperature and may denature in extreme heat.
The independent variable of this lab is the condition of the liver, heated or ground.
The dependent variable is a measure of the oxygen gas bubbles produced (cm) in the test tubes.
Procedure: First,five clean test tubes (16mmx 150mm size) were placed in a test tube rack and numbered one through five. Then, 10mL of H2O2 (hydrogen peroxide) was measured using a graduated cylinder and added to test tube number one. A ruler was used to measure any bubbles (oxygen gas) produced. A 2 gram (g) piece of room temperature liver was massed out on a balance. The liver was placed into test tube number two. Another 10mL of H2O2was measured with a graduated cylinder and added to the test tube. A ruler was used to measure any bubbles (oxygen gas) produced. Next, 1 g of sand was massed out on a balance and added to test tube number three. Another 10mL of H2O2was measured with a graduated cylinder and added to the test tube. A ruler was used to measure any bubbles (oxygen gas) produced. Test tubes number one through three were used as part of the experimental controls to serve as comparisons. Another 2 g piece of liver was massed out on the balance and then placed in a mortar and pestle. To aid in mashing the liver, 1 g of sand was massed out on the balance and added to the mortar. The liver was crushed into a paste and then placed in test tube number four. Another 10mL of H2O2was measured with a graduated cylinder and added to the test tube. A ruler was used to measure any bubbles (oxygen gas) produced. A final 2 g piece of liver was massed out on the balance and then placed into a hot water bath set at 100°C for five minutes. After five minutes, the liver was removed and placed into test tube number five. Another 10mL of H2O2was measured with a graduated cylinder and added to the test tube. A ruler was used to measure any bubbles (oxygen gas) produced.
Data:
Table 1
Oxygen Gas Produced by Liver Enzymes Breaking Down Hydrogen Peroxide
Contents of test tube / Height of oxygen bubbles produced (cm)1)10 mL of Hydrogen Peroxide / 0
2)10 mL of Hydrogen Peroxide and 2 grams of liver / 12
3)10 mL of Hydrogen Peroxide and 1 gram of sand / 0
4)10 mL of Hydrogen Peroxide and 2 grams of liver ground with 1 gram of sand / 23
5)10 mL of Hydrogen Peroxide and 2 grams of cooked liver / 0
Table 1 Caption: The above table shows the varying amounts of oxygen gas produced when hydrogen peroxide was introduced to pieces of liver in varying forms; whole, ground, and cooked. Results for hydrogen peroxide alone and sand alone are also shown.
Figure 1
Figure 1 Caption: The above graph shows the varying amounts of oxygen gas produced when hydrogen peroxide was introduced to pieces of liver in varying forms; whole, ground, and cooked. Results for hydrogen peroxide alone and sand alone are also shown.
Conclusion:
What is the impact of changing temperature or surface area on the ability of an enzyme to function?
If hydrogen peroxide is added to a sample of liver that was exposed to heat or had its surface area changed by grinding, then the enzyme function of the heated piece of liver will be reduced as measured by fewer oxygen gas bubbles produced because enzymes are sensitive to changes in temperature and may denature in extreme heat.
The hypothesis was supported by the data. As shown in Table 1, the liver that was heated produced 0 cm of gas. This shows that no enzymes were reacting. The high heat exposed to the liver caused the enzymes to denature (essentially change shape) preventing the release of gas caused by the breakdown of hydrogen peroxide. The same result of 0 cm of gas was seen with the hydrogen peroxide alone and the sample containing sand only. These three samples did not contain enzymes capable of causing a reaction. It was expected that the hydrogen peroxide alone and the sand would not produce a reaction. The sand was tested to ensure that any reaction with the ground liver was in no way impacted by the addition of the sand to the sample. The sample that produced the most oxygen gas was the liver ground with sand. As shown in Figure 1, the ground liver produced more than double the gas as the whole piece of liver. Whole liver produced 12cm of gas while ground liver produced 23 cm of gas. The increased reaction is likely due to more enzymes in the liver being exposed and capable of reacting with hydrogen peroxide. The amount of surface area of the whole piece of liver compared to the increased surface area of the ground liver paste allowed more breakdown of H2O2 to oxygen gas and water. Testing the whole piece of liver intact acted as a point of comparison (control) in which to show how changing the surface area would impact the results of the reaction.
To increase the validity of the lab, several constants were in place. The same amount of liver (2 g) was used for each test, the same amount of hydrogen peroxide (10 mL) was added to each sample, the same type of liver (from a cow) was used for all tests, the same size test tubes (16mmx150mm) were used to ensure comparable measurements of gas produced.
In future experiments on this topic, it would be helpful to formulate a more accurate method for measuring the exact amount of gas produced by the breakdown of hydrogen peroxide. Measuring the height of the gas bubbles produced in the same size test tubes provided an adequate comparison but could be more accurate. Future tests could also investigate the impact of different liver samples from different organisms and/or different food samples like chicken or potatoes for the presence of the enzyme capable of breaking down hydrogen peroxide.
Citations:
Freuman, T. (2013, April 23). Digestive enzymes: Help or hype?. Retrieved from
Science Buddies. (2012, March 08). The liver: Helping enzymes help you! . Retrieved from