Solved by a verified expert:Your Full Name:Biology 102/103Lab 4: EnzymesINSTRUCTIONS:On your own and without assistance, complete this Lab 4 Answer Sheetelectronically and submit it via the Assignments Folder by the date listed in the CourseSchedule (under Syllabus).To conduct your laboratory exercises, use the Laboratory Manual located underCourse Content. Read the introduction and the directions for each exercise/experimentcarefully before completing the exercises/experiments and answering the questions.Save your Lab 4 Answer Sheet in the following format: LastName_Lab4 (e.g.,Smith_Lab4).You should submit your document as a Word (.doc or .docx) or Rich Text Format(.rtf) file for best compatibility.Pre-Lab Questions1. How could you test to see if an enzyme was completely saturated during anexperiment?2. List three conditions that would alter the activity of an enzyme. Be specific withyour explanation.3. Take a look around your house and identify household products that work bymeans of an enzyme. Name the products, and indicate how you know they workwith an enzyme. Experiment 1: Enzymes in FoodThis experiment tests for the presence of amylase in food by using Iodine-PotassiumIodide, IKI. IKI is a color indicator used to detect starch. This indicator turns dark purpleor black in color when in the presence of starch. Therefore, if the IKI solution turns to adark purple or black color during the experiment, one can determine that amylase is notpresent (because presence of amylase would break down the starch molecules, and theIKI would not change color).Materials(1) 2 oz. Bottle (Empty)*2 Food Products (e.g., ginger root,(1) 100 mL Graduated Cylinderapple, potato, etc.)30 mL Iodine-Potassium Iodide, IKI *Kitchen KnifePermanent Marker*Paper TowelRuler*Saliva Sample2 Spray Lids*Tap Water30 mL Starch (liquid)*Cutting Board*You Must ProvideProcedure:1. Remove the cap from the starch solution. Attach the spray lid to the starchsolution.2. Rinse out the empty two ounce bottle with tap water. Use the 100 mL graduatedcylinder to measure and pour 30 mL of IKI into the empty two ounce bottle.Attach the remaining spray lid to the bottle.3. Set up a positive control for this experiment by spraying a paper towel with thestarch solution. Allow the starch to dry for approximately one hour (this timeinterval may vary by location).4. In the mean time, set up a negative control for this experiment. Use yourknowledge of the scientific method and experimental controls to establish thiscomponent (hint: what should happen when IKI solution contacts something thatdoes not contain starch?) Identify your negative control in Table 1.Note: Be sure to space the positive and negative controls apart from each otherto prevent cross-contamination. 5. When the starch solution has dried, test your positive and negative controls. Thisstep establishes a baseline color scale for you to evaluate the starchconcentration of the food products you willtest in Steps 7 – 11. Record your results inTable 1.6. Select two food items from your kitchencabinet or refrigerator.7. Obtain a kitchen knife and a cutting board.Carefully cut your selected food items tocreate a fresh surface.8. Gently rub the fresh/exposed area of thefood items on the dry, starch-sprayed papertowel back and forth 10 – 15 times. Labelwhere each specimen was rubbed on theFigure 3: Sample set-up.paper towel with a permanent marker(Figure 3).9. Wash your hands with soap and water.10. Take your finger and place it on your tongue to transfer some saliva to yourfinger. Then, rub your moistened finger saliva into the paper towel. Repeat thisstep until you are able to adequately moisten the paper towel.Note: You should always wash your hands before touching your tongue!Alternatively, if you do not wish to put your hands in your mouth, you may alsoprovide a saliva sample by spitting in a separate bowl and rubbing the papertowel in the saliva. Be sure not to spit on the paper towel directly as you mayunintentionally cross-contaminate your samples.11. Wait five minutes.12. Hold the IKI spray bottle 25 – 30 cm away from the paper towel, and mist with theIKI solution.13. The reaction will be complete after approximately 60 seconds. Observe wherecolor develops, and consider what these results indicate. Record your results inTable 1.Table 1: Substance vs. Starch PresenceSubstancePositive Control: StarchNegative Control: Student MustSelectFood Product:Food Product:Saliva:Resulting ColorPresence of Starch? Post-Lab Questions1. What were your controls for this experiment? What did they demonstrate? Why wassaliva included in this experiment?2. What is the function of amylase? What does amylase do to starch?3. Which of the foods that you tested contained amylase? Which did not? Whatexperimental evidence supports your claim?4. Saliva does not contain amylase until babies are two months old. How could thisaffect an infant’s digestive requirements? 5. There is another digestive enzyme (other than salivary amylase) that is secreted bythe salivary glands. Research to determine what this enzyme is called. Whatsubstrate does it act on? Where in the body does it become activated, and why?6. Digestive enzymes in the gut include proteases, which digest proteins. Why don’tthese enzymes digest the stomach and small intestine, which are partially composedof protein?Experiment 2: Effect of Temperature onEnzyme ActivityYeast cells contain catalase, an enzyme whichhelps convert hydrogen peroxide to waterand oxygen. This enzyme is very significant ashydrogen peroxide can be toxic to cells if allowedFigure 4: Catalase catalyzes thedecomposition of hydrogen peroxideto water and oxygen. to accumulate. The effect of catalase can be seen when yeast is combined withhydrogen peroxide (Catalase: 2 H2O2 → 2 H2O + O2).In this lab you will examine the effects of temperature on enzyme (catalase) activitybased on the amount of oxygen produced. Note, be sure to remain observant foreffervescence when analyzing your results.Materials(2) 250 mL Beakers3 Balloons30 mL 3% Hydrogen Peroxide,H2O2Measuring SpoonPermanent MarkerRuler20 cm String3 Test Tubes (Glass)Test Tube RackThermometerYeast Packet*Hot Water Bath*Stopwatch*You Must ProvideProcedure1. Use a permanent marker to label test tubes 1, 2, and 3. Place them in the testtube rack.2. Fill each tube with 10 mL hydrogen peroxide. Then, keep one of the test tubes inthe test tube rack, but transfer the two additional test tubes to two separate 250mL beakers.3. Find one of the balloons, and the piece of string. Wrap the string around theuninflated balloon and measure the length of the string with the ruler. Record themeasurement in Table 2.4. Create a hot water bath by performing the following steps:a. Determine if you will use a stovetop or microwave to heat the water. Usethe 100 mL graduated cylinder to measure and pour approximately 200mL of water into a small pot or microwave-safe bowl (you will have tomeasure this volume in two separate allocations).b. If using a stovetop, obtain a small pot and proceed to Step 4c. If using amicrowave, obtain a microwave-safe bowl and proceed to Step 4e.c. If using a stove, place a small pot on the stove and turn the stove on to amedium heat setting.d. Carefully monitor the water in the pot until it comes to a soft boil(approximately 100 °C). Use the thermometer provided in your lab kit toverify the water temperature. Turn the stove off when the water begins to boil. Immediately proceed to Step 5.CAUTION: Be sure to turn the stove off after creating the hot water bath.Monitor the heating water at all times, and never handle a hot pan withoutappropriate pot holders.e. If using a microwave, place the microwave-safe bowl in the microwaveand heat the water in 30 second increments until the temperature of thewater is approximately 100 °C. Use the thermometer provided in your labkit to verify the water temperature. Wait approximately one minute beforeproceeding to Step 5.5. Place Tube 1 in the refrigerator. Leave Tube 2 at room temperature, and placeTube 3 in the hot water bath.Important Note: The water should be at approximately 85 °C when you placeTube 3 in it. Verify the temperature with the thermometer to ensure the water isnot too hot! Temperatures which exceed approximately 85 °C may denature thehydrogen peroxide.6. Record the temperatures of each condition in Table 2. Be sure to provide thethermometer with sufficient time in between each environment to avoid obscuringthe temperature readings.7. Let the tubes sit for 15 minutes.8. During the 15 minutes prepare the balloons with yeast by adding ¼ tsp. of yeasteach balloon. Make sure all the yeast gets settled to the bulb of the balloon andnot caught in the neck. Be sure not spill yeast while handling the balloons.9. Carefully stretch the neck of the balloon to help ensure it does not rip whenstretched over the opening of the test tube.10. Attach the neck of a balloon you prepared in step 8 to the top of Tube 2 (theroom temperature test tube) making sure to not let the yeast spill into the testtube yet. Once the balloon is securely attached to the test tube lift the balloonand allow the yeast to enter the test tube. Tap the bulb of the balloon to ensureall the yeast falls into the tube.11. As quickly and carefully as possible remove the Tube 1 (cold) from therefrigerator and repeat steps 9 – 10 with Tube 1 using a balloon you prepared instep 8.12. As quickly and carefully as possible remove Tube 3 (hot) from the hot water bathand repeat steps 9 – 10 with Tube 3 using a balloon you prepared in step 8.13. Swirl each tube to mix, and wait 30 seconds.14. Wrap the string around the center of each balloon to measure the circumference.Measure the length of string with a ruler. Record your measurements in Table 2.Table 2: Balloon Circumference vs. TemperatureTubeTemperature(°C)Balloon Circumference(Uninflated; cm)Balloon Circumference(Final; cm) 1 – (Cold)2 – (RT)3 – (Hot)Post-Lab Questions1. What reaction is being catalyzed in this experiment?2. What is the enzyme in this experiment? What is the substrate?3. What is the independent variable in this experiment? What is the dependentvariable?4. How does the temperature affect enzyme function? Use evidence from your data tosupport your answer.5. Draw a graph of balloon diameter vs. temperature. What is the correlation? 6. Is there a negative control in this experiment? If yes, identify the control. If no,suggest how you could revise the experiment to include a negative control.7. In general, how would an increase in substrate alter enzyme activity? Draw a graphto illustrate this relationship.8. Design an experiment to determine the optimal temperature for enzyme function,complete with controls. Where would you find the enzymes for this experiment?What substrate would you use?
Recent Comments