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QuestionLEARNING OBJEC TIVES Upon the completion of these experiments the…LEARNING OBJEC TIVESUpon the completion of these experiments the student will be able to:•     Describe the function of an enzyme and explain the role of the active site in enzyme specificity and activity.•     Identify the substrate, enzyme, and products in the chemical reaction studied today.•     Predict the effect of various temperatures on enzyme activity.•     Predict the effect of various enzyme concentrations on enzyme activity.•     Predict the effect of various pH conditions on enzyme activity.•      MATERIALS•     Provided in your kit: 3 small test tubes, two plastic cups with marking, 1 graduated cylinder, yeast powder, disposable pipettes,•     Provided by you: small ruler, teaspoon measurer, bottle of soap or dish detergent solution; baking soda powder, vinegar, hydrogen peroxide (H2O2), sharpie or marker, small plastic containers or cups  INTRODUC TIONThe cell carries out many chemical reactions. The sum total of all the chemical reactions that occur in a cell (or organism) is known as metabolism. For example, examine the following:Molecule A + Molecule BReactants                                  ProductsIn a chemical reaction the atoms of the reactant molecules are rearranged to make the product molecules. In living systems, most reactions do not happen spontaneously, but instead require the assistance of an enzyme. An enzyme is a protein molecule that participates in a chemical reaction, but is not changed by the reaction. Therefore, enzymes can be used over and over again.The active site of an enzyme is a location on the protein that allows the substrate to fit both three dimensionally and electrically. In this way, the enzyme and substrate come together and the reaction occurs at the active site. In this position the enzyme lowers the amount of energy that is necessary to start the reaction. This is called the energy of activation.After the reaction takes place, the product leaves the enzyme and then the enzyme can be used again. Enzymes participate in nearly every chemical reaction that occurs in cells, for example: during a degradation reaction, the substrate is broken down. During a synthesis reaction, however,substrates combine to produce the product(s). We will experiment with a degradation reaction in this laboratory activity.Because enzymes are specific to only one substrate, enzymes are only capable of catalyzing one reaction. This concept is known as enzyme specificity. Enzyme specificity is a result of the three- dimensional shape of the active site and the complementary electrical conditions of the active site and the substrate. This idea was once called the lock and key mechanism of enzyme activity. The more modern name for this is the induced fit model of enzyme function.Enzyme + Substrate             Enzyme Substrate Complex             Enzyme + ProductFigure 6.1: Enzyme substrate reaction.A degradation reaction is represented in Figure 6.1 above. During degradation reactions the substrate is broken down into two products. Notice how the shape of the enzyme accommodates its substrate. The location where the enzyme and substrate form an enzyme-substrate complex is called the active site because the reaction occurs here.At the end of the reaction, the product is released, and the enzyme can then combine with another substrate molecule. A cell needs only a small amount of an enzyme because enzymes are used over and over again. Some enzymes have turnover rates well in excess of a million product molecules per minute.All enzymes are complex proteins that generally act in an organism’s closely controlled internal environment, where the temperature and pH remain within a narrow range. Extremes in pH or temperature may denature the enzyme by permanently altering its three-dimensional chemical structure. Even a small change in the protein’s structure will change the enzyme’s shape enough to prevent formation of the enzyme-substrate complex, and thus keep the reaction from occurring. As more substrate molecules fill active sites, more product results per unit time. Therefore, in general, an increase in enzyme or substrate speeds enzymatic reactions. In this laboratory, you will test the effect of temperature, enzyme concentration, and pH on an enzymatic reaction.Enzymes work best within a limited range of conditions such as temperature and pH. This is one of the aspects of homeostasis or the tendency of cells to maintain relatively constant internal environmental conditions.PRE-L AB QUESTIONSHydrogen peroxide is a harmful byproduct of many normal metabolic processes; to prevent damage to cells and tissues, it must be quickly converted into other, less dangerous substances. To thisend, catalase, an enzyme we will study in this lab, is frequently used by cells to rapidly catalyze the decomposition of hydrogen peroxide into less-reactive gaseous oxygen and water molecules.Catalases are some of the most efficient enzymes found in cells. Each catalase molecule can decompose millions of hydrogen peroxide molecules every second. In mammals, catalase is found predominantly in the liver and particularly in the peroxisomes of those and other cells.In the experimental procedures that follow, you will be working with the enzyme catalase. Catalase is present in cells where it speeds the breakdown of the toxic chemical hydrogen peroxide to water and oxygen, as shown by the following equation:2H2O2Catalase2H2O + O2Hydrogen Peroxide                                                             Water     OxygenThe activity of the catalase will be represented by the amount of O2 produced.1.          What is the reactant in this reaction?                   2.          What is the substrate for catalase?                      3.          What are the products in this reaction?               and                 4.          Explain how most enzymes react to boiling, specifically catalase, in the first activity.5.          After reading Activity 2, explain what happens to the behavior of enzymatic reactions when insufficient enzyme is present.6.          In which structure is catalase stored in cells?7.          How does pH influence the reactivity of an enzyme? What does optimal environment for an enzyme mean?Prepare Yeast Solution (Source for Catalase) For All Activities:Yeast cells, like most other cells, contain the enzyme catalase in the cells, so in this lab exercise, we will use yeast solution as the source for catalase.1.    Label one of plastic cup with “yeast” and put it on your workstation (kitchen table, counter top.).2.    Add ¼ tsp of dry active yeast into the cup, followed by 100 ml of tap water in the cup using the graduation markings on the cup.3.    Add about three drops of liquid soap or dish detergent into the cup and stir it with a disposable pipet to mix. This is the prepared yeast solution for the catalase source. Leave the disposable pipet in this cup and dedicate it to this solution only throughout the entire exercise.4.    Proceed to the following activities.ACTIVITY #1 – EFFECT OF TEMPERATURE ON ENZYME ACTIVITYIn general, cold temperatures slow chemical reactions, and warm temperatures speed chemical reactions. Usually the rate of an enzymatic reaction doubles with every 10oC rise in temperature. Very high temperatures, usually greater than 65 degrees Celsius, cause an enzyme to denature in a way that inactivates it. Denaturing means that the three-dimensional structure is permanentlyaltered and therefore the active site will no longer accommodate the substrate, thus inactivating the enzyme. Please read more in your textbook for clarification.HypothesisHypothesize about the activity of catalase at various temperatures.Procedure #11.          Label three test tubes as follows: C- for cold temperature, R- for room temperature, and H- for hot temperature. Put all the tubes in the second plastic cup.2.         Use the graduated cylinder and the pipet in the yeast solution, measure out 2 ml of the yeast (catalase) solution and pour it into each of the three test tubes, make sure that you mix the solution by stirring with the pipet each time before measuring.3.          Put the C- tube in a cup or a container in the fridge to cool it down; and put the H-tube in a container and pulse for 5 seconds in a microwave oven, repeat on more time to heat it up. Be careful, 5 seconds each, no more; and leave the R-tube on your workstation.4.          Set your timer at 30 second.5.         Measure out 2 ml of H2O2 with the graduated cylinder and pour it into the R-tube, and start the timer right away.6.         At 30 seconds mark, use the small ruler, measure the O2 bubble produced and record the data in the table below. Be sure to measure the height of the bubble produced, don’t include the liquid part. See figure on next page)(If at 30 seconds, the bubble overflows, then time for 20 seconds instead of 30seconds, and use this time for all the rest of activities)7.          Repeat steps 4-6 with the H-test tube.8.          By now, the C-tube should be cold already, if not, leave it in the fridge for a few more minutes. Then, repeat steps 4-6 with the C-test tube, and record the data in the table.9.          Rinse the test tubes and graduated cylinder under tap water and blot dry using paper towels for the next activity.Flat-bottom vial     Oxygen bubbles – use the ruler to measure this column  Catalase and hydrogen peroxide solutionsFigure 6.2: Flat bottom vial with catalase and hydrogen peroxide solutions reacting Table 6.1: Comparison of the Action of Catalase at Three Temperatures on Hydrogen Peroxide.Catalase TemperatureOxygen (O2) Bubble Height (cm)Cold TemperatureRoom TemperatureHot TemperatureCONCLUSIONThe amount of bubbling corresponds to the degree of enzyme activity. As the reaction between hydrogen peroxide and catalase proceeds, oxygen is produced and it is visualized by using the soap and the creation of bubbles.What is the dependent variable in this experiment?What is the independent variable in this experiment?What is your conclusion concerning the effect of temperature on enzyme activity?ACTIVITY #2 – EFFECT OF INCREASING CATALASE CONCENTRATION IN AN ENZYMATIC REACTIONIn general, a higher enzyme or substrate concentration results in faster enzyme activity – that is,  the amount of product per unit time for any particular reaction will increase. If there is insufficient enzyme present, an enzymatic reaction will not proceed as fast as it otherwise would because all ofthe active sites of the available enzyme are occupied with the reaction. Additional active sites could speed up the reaction. As the amount of enzyme is increased, the rate of reaction increases. If there are more enzyme molecules than are needed, adding additional enzyme will not increase the rate. So at low enzyme concentration there is great competition for the active sites and the rate of reaction is low. As the enzyme concentration increases, there are more active sites and the reaction can proceed at a faster rate. Reaction rate therefore initially increases as enzyme concentration increases, but then it levels off.Eventually, increasing the enzyme concentration beyond a certain point has no effect because thesubstrate concentration becomes the limiting factor as illustrated in Figure 6.4 below.Enzyme ConcentrationFigure 6.4: Amount of product generated begins to level off with increased enzyme concentration.In this investigation, we will examine what happens to the amount of oxygen generated when the amount of enzyme is increased while holding the concentration of substrate equal.HypothesisHypothesize about the activity of catalase at various concentrations.Procedure #21.          Use the three clean test tubes and label each with 1, 2, and 3.2.          Use the graduated cylinder, measure out and add 2mL of hydrogen peroxide into each test tube.3.          Using the disposable pipet and graduated cylinder, measure out 1 ml of the yeast catalase solution and add to tube 1.  Begin timing for 30 seconds immediately.4.          At the 30 seconds mark, using the small ruler measure the height of the column of O2 bubble and record the data in the table below.5.          Repeat steps 3 and 4 but with 2ml of yeast catalase solution of tube 2, and use 3 ml of yeast catalase solution for tube 3. Record the data in the tableSo, in summary:   tube 1: 1 ml of yeast catalase solution                                tube 2: 2 ml of yeast catalase solution                                tube 3: 3 ml of yeast catalase solution6.          Clean the test tubes and graduated cylinder by rinsing under tap water and blot dry with paper towel. Table 6.2: Effect of Catalase Concentration on Reactivity with Hydrogen Peroxide.Catalase Relative Concentration (ml)Oxygen (O2) Bubble Height (cm)123ACTIVITY #3 – EFFECT OF pH ON ENZYME ACTIVITYEnvironmental pH can also influence the three-dimensional shape of an enzyme. Every enzyme has an optimum pH at which it is most active. In this investigation, we will examine the activity of catalase at three different pH values.HypothesisHypothesize about the rate of activity of catalase at various pHs.Procedure #31.          Obtain three, clean test tubes and mark them #1-3.2.         Using a clean pipette and graduated cylinder, add 2 mL of yeast catalase solution to each tube. Remember to mix the solution before each measuring.3.          Rinse the graduated cylinder and measure out 2ml of vinegar and pour into tube 1. Mix by swirling the tube.4.          Measure out 2 ml of tap water and add to tube 2, mix5.          Measure out ¼ tsp of baking soda powder and add to 2 ml of water and stir to dissolve the baking soda powder and add the solution to tube 3.6.          Using the pH paper, dip one end into tube 1 for a couple of seconds, take it out and read the pH; use a new pH paper each time with tubes 2 and 3. Record the pH data in the table below.7.          Using a clean disposable pipette and graduated cylinder, add 2 mL of H2O2 into tube 1 and start your timer immediately for 30 seconds.8.          After 30 seconds, using the small ruler, measure the height of oxygen bubble column and record the data in the table.9.          Repeat steps 7-8 with tube 2 and 3.  Record the data in the table.      Table 6.3: Effect of pH on Catalase Activity. Tube IDpH Oxygen (O2) Bubble Height (cm)12 3ScienceBiologyBIO 101Share Question