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L. Paparella Sullivan West Living Environment Factors Affecting the Rate of Enzyme Reaction in Liver Name:_____________________________________________ Date:__________ Introduction: All organisms rely on enzymes to catalyze chemical reactions. An enzyme is a biological catalyst that increases the rate of chemical reaction by lowering the level of activation energy necessary to start the reaction. Without enzymes, many of the chemical reactions that occur within living things would proceed too slowly to be useful. Enzymes speed up these reactions by bringing the reactants into close proximity and helping their interaction. Liver contains a specific enzyme called catalase. When hydrogen peroxide (H2O2) is added to liver, a chemical reaction occurs which results in the products of oxygen gas (O2) and liquid water (H2O). Pre-Lab Questions: Use complete sentences. 1. What is an enzyme?______________________________________________________ _____________________________________________________________________________ 2. What is an enzyme’s function?____________________________________________ __________________________________________________________________________ 3. What would happen if we did not have enzymes?_________________________ _________________________________________________________________________ 4. What is the name of the enzyme found in liver? ______________________________ _____________________________________________________________________________ 5. What is the name of the substance that we will be reacting with the liver enzyme? ________________________________________________________________________ 6. What are the names and formulas of the products that you will see if the reaction is occurring?_____________________________________________________________ ______________________________________________________________________ 7. If an enzyme fits with its substrate, the reaction will occur. If something is done to change the shape of the ____________________, it will not fit the ____________________________ and the reaction will not happen. In this lab the substrate is the chemical ________________________and its chemical formula is _______________. In this lab we will testing the effect of different factors on the enzyme’s ability to interact with the substrate. List 4 things that you think might effect the enzyme’s ability to work properly. _______________________________________________________________ ________________________________________________________________________ L. Paparella Sullivan West Procedure For Part 1: Testing Surface area and Temperature Living Environment 1. Using a blender, I pureed a chunk of chicken liver. This step will change the ______________________________ of the liver and expose more of the enzyme ________________ to the substrate________________________. Some of the puree was put on ice and some was microwaved in water until hot. Some was left at room temperature. 2. Put your spot plate on a piece of paper. Label the top left side of the paper as Ice/Puree, the top middle as Room /Puree and the top right as Hot/Puree. Label the bottom left side as Ice/Chunk, the bottom middle as Room /Chunk and the bottom right as Hot/Chunk. 3. You will record your observations in the Data Table below. Add 5 drops of hydrogen peroxide (H2O2 ) to the first spot of puree. Record how many seconds it bubbles for = reaction rate) Note if foam (oxygen bubbles in water) is produced quickly or slowly and use ++++ for lots of bubbles/foam and + for very little foam= enzyme activity) If nothing happens, record that. 4. Repeat this for the other ice cold chunk of liver and then the other set ups. Data Table 1: Effect of Temperature and Surface Area on Enzyme Reaction Time Ice Cold Temp /Liver Room Temp/ Liver Hot Temp / Liver Puree Puree Puree Ice/Chunk Liver Room Temp/Chunk Liver Hot Temp/ Chunk Liver Analysis for Part 1: 1. What is meant by reaction rate? ______________________________________ 2. What are we using to measure the reaction rate? _________________________ 3. How are we comparing the enzyme activity? _____________________________ 4. What can you conclude about temperature and enzyme reaction rate? ____________________________________________________________________ ____________________________________________________________________ 5. What can you conclude about surface area and enzyme reaction rate? ______________________________________________________________________ L. Paparella Sullivan West Procedure for Part 2: Testing pH Conditions: Living Environment 1. Place your spot plate on a piece of paper and label the top left side of the paper “Vinegar”, the top middle of the paper “water” and the top right side “Borax”. Place a chunk of liver that has been soaked in either the vinegar, water or borax in the 3 spots: left, middle and right side of the spot plate. 2. Record the pH of each liquid soaking solution /liver sample in the data table below. Then circle the Acid, Base or Neutral based on the pH scale reading. 1-6 acid, 7 is neutral, 8-14 is base. 3. Add 5 drops of H2O2 to the liver on the left side marked vinegar and record your observations in the data table. (record how much it bubbles= enzyme activity = use ++++ for lots of bubbles, ++ for a few bubbles , + for very few bubbles) Record the time that the bubbles lasted= reaction rate. 4. Repeat for the other two samples of liver that have soaked in water or borax. Data Table : Effect of pH on Enzyme Reaction Rate Vinegar Solution Water Solution Borax Solution pH level:_______ pH level:_______ pH level:_______ Acid, Base or Neutral Acid, Base or Neutral Acid, Base or Neutral Observations: Observations: Observations: Analysis Questions: 1. What was the effect of the pH change on the reaction rate? Be specific. Which pH level gave the optimal result? Which pH gave the worst result? __________________________________________________________________________________ __________________________________________________________________________________ 2. Which condition of all tested gave the fastest reaction time? ___________________________________________________________________________ 3. Which condition destroyed the enzyme completely?______________________________ 4. Which condition of all tested gave the slowest reaction time? _____________________________________________________________ 5. What was the effect of increasing the surface area? Compare the chunk at room temp. with the puree at room temp. _________________________________________________ ____________________________________________________________________________ L. Paparella Sullivan West Additional Notes: compiled by C. Diehl Living Environment Hydrogen peroxide (H2O2) is a very pale blue liquid, slightly more viscous than water, that appears colorless in dilute solution. It is a weak acid, has strong oxidizing properties, and is a powerful bleaching agent. It is used as a disinfectant, antiseptic, oxidizer, and in rocketry as a propellant.[2] The oxidizing capacity of hydrogen peroxide is so strong that it is considered a highly reactive oxygen species. Hydrogen peroxide is naturally produced in organisms as a byproduct of oxygen metabolism. Nearly all living things possess enzymes known as peroxidases, which harmlessly and catalytically decompose low concentrations of hydrogen peroxide to water and oxygen. Biological function Hydrogen peroxide is also one of the two chief chemicals in the defense system of the bombardier beetle, reacting with hydroquinone to discourage predators. A study published in Nature found that hydrogen peroxide plays a role in the immune system. Scientists found that hydrogen peroxide is released after tissues are damaged in zebra fish and this is thought to act as a signal to white blood cells to converge on the site and initiate the healing process. When the genes required to produce hydrogen peroxide were disabled, white blood cells did not accumulate at the site of damage. Although the experiments were conducted on fish, they are genetically similar to humans and so this may also be applicable to humans. Asthma sufferers have higher levels of hydrogen peroxide in their lungs than healthy people and this could explain why asthma sufferers have inappropriate levels of white blood cells in their lungs.[18][19] http://en.wikipedia.org/wiki/Hydrogen_peroxide On the next page complete the worksheet by labeling / identifying the enzymes/ substrates and >>>products of various biological reactions. L. Paparella Sullivan West Living Environment Use the following terms to label the 4 diagrams below. protease/protein >>> amino acids Lipase/lipid>>>> glycerol and fatty acid Carbohydrase/ starch>>>> simple sugars Catalase/hydrogen peroxide>>>>> water and oxygen You will need to know these for your test on __________________.