AP Biology Lab Reports

Catalysis Lab Report

Data and Results:

Introduction:
               Enzymes are proteins, which is one of the four macromolecules (Carbohydrates, Proteins, Lipids, and Nucleic acids). Enzymes are made in the ribosomes of cells to be catalysts in chemical reactions. The purpose of enzymes is to lower the activation energy (the amount energy required to begin a reaction) of reactions. In enzyme-catalyzed reactions a substrate is the substance acted on by the enzyme, and joins the enzyme at the activation site to either be hydrolyzed  (Catabolic) or synthesized (Anabolic) with other molecules, resulting in a product. Each activation site is unique to a substrate, and this reaction can be reversed. During this reaction an enzyme remains the same and can be reused. Enzymes are only effective under certain environmental conditions because disruptions in temperature, pH, and salt concentration can denature (the process by which proteins are altered at the quaternary, tertiary, and secondary structure levels) an enzyme, rendering it useless.
Catalase is crucial in protecting living cells from oxidative damage ( http://www.ebi.ac.uk/interpro ). Catalase is made of four polypeptide chains and each of the chains is over 500 amino acids in length ( http://www.sinobiological.com/Catalase-a-5136.html). The optimal temperature for catalase varies between different species.
In this lab experiment, beef liver will be puréed, and used to test the reaction between the Catalase within the liver and hydrogen peroxide. Catalase is a very common enzyme that can be found in most living things exposed to oxygen. In most organisms catalase is in every organ but really high concentrations are found in the liver. If Catalase is present within the beef liver, then the hydrogen peroxide will bubble creating water and oxygen. Catalase is responsible for the decomposition of hydrogen peroxide in living organisms, resulting in the products water and oxygen through bubbling. In activity A the objective is to determine the effect of boiling on how well Catalase function. If Catalase is boiled then it won't work because it would be denatured. In activity C and D the objective is to determine the uncatalyzed and catalyze rate of decomposition of hydrogen peroxide. Also,in activity D the rate of catalyzed decomposition is in different time intervals. If all five cups had equal hydrogen peroxide then the one with the longest time should have less hydrogen peroxide because it had more time for decomposition to occur.

Materials and Method:
          Samples of kidney, heart, or liver are needed to isolate Catalase. Materials for the lab include a H2O2, 60ml. cup, test tube plus holder, syringe for the hydrogen peroxide, pipers for transferring, wash plus waste water cups, and some liver. Take about 5-10 grams of liver and blend with 500ml of distilled and unchlorinated water.Blend until uniform (homogeneous).Take a milliliter of this Catalase solution, and put it in a test tube.Then add 10ml. of hydrogen peroxide to the same test tube holding the Catalase solution. If there is Catalase, foaming should occur. This foam has a lot of oxygen due to the Catalase breaking down the hydrogen peroxide.The more foam equals more Catalase present. This experiment can be conducted with any other type of meat such as kidney or heart.

                                                               Conclusion:
         The experiments did determine there was Catalase present in the beef liver because it foamed when it contacted hydrogen peroxide. When the Catalase was boiled and then added to hydrogen peroxide no reaction occurred because the boiling rendered it useless. The uncatalyzed rate of decomposition of hydrogen peroxide was determined to be 2.7 ml/24 hours. In activity D five cups were all filled with 10ml. of hydrogen peroxide and filled with catalase for time intervals of either 10,30,60,120, or 180 seconds. To stop the reactions at the specific time, sulfuric acid was added to neutralize/halt the reaction from progressing. This could happen because sulfuric acid denatured the enzyme. The individuals cups were then titrated to determine how much hydrogen peroxide decomposed. After titration it was determined that more hydrogen peroxide decomposed if the reaction went longer. The results ranged from 2.3ml. at 10 sec. to 2.6ml. at 180 sec.Through experimentation the hypotheses presented were determined to be accurate. The results and experiments were not perfect because errors do occur such as over titrating, accidentally spilling contents from syringe or cups, misreading values on syringes and cups, and etc. These errors can be reduced and prevented by being more careful when handling the pipers and syringes. Also letting multiples people read the syringes and cups for better accuracy.