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biology questions




Question;Experiment 1;Enzymes in Food;Amylase is used by;humans to facilitate digestion. Specifically, it is an enzyme which breaks down;starch molecules into sugar molecules. This is why people sometimes observe a;sweet taste after sucking on a starch-containing food for an extended period of;time. Amylase is found naturally in human saliva and the pancreas. However, it;is also present in some of the common plant foods consumed by humans.;This experiment;tests for the presence of amylase in food by using Iodine-Potassium Iodide;IKI. IKI is a color indicator used to detect starch. This indicator turns dark;purple or black in color when in the presence of starch. Therefore, if the IKI;solution turns to a dark purple or black color during the experiment, one can determine;that amylase is not present (because presence of amylase would break down the;starch molecules, and the IKI would not change color).;Materials;(1) 2 oz. Bottle (Empty);(1) 100 mL Graduated Cylinder;30 mL Iodine-Potassium Iodide, IKI;Permanent Marker;Ruler;2 Spray Lids;30 mL Starch (liquid);*Cutting Board;*2 Food Products (e.g.;ginger root, apple, potato, etc.);*Kitchen Knife;*Paper Towel;*Saliva Sample;*Tap Water;*You Must Provide;Procedure;1.;Remove the cap from the starch solution. Attach the spray lid to;the starch solution.;2.;Rinse out the empty two ounce bottle with tap water. Use the 100;mL graduated cylinder 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 the starch solution. Allow the starch to dry for approximately one;hour (this time interval may vary by location).;4.;In the mean time, set up a negative control for this experiment.;Use your knowledge of the scientific method and experimental controls to;establish this component (hint: what should happen when IKI solution contacts;something that does not contain starch?) Identify your negative control in;Table 1.;Note: Be sure to space the positive and negative controls apart from;each other to prevent cross-contamination.;5.;When the starch solution has dried, test your positive and;negative controls. This step establishes a baseline color scale for you to;evaluate the starch concentration of the food products you will test in Steps 7;- 11. Record your results in Table 1.;6.;Select two food items from your kitchen cabinet or refrigerator.;7.;Obtain a kitchen knife and a cutting board. Carefullycut;your selected food items to create a fresh surface.;Figure 3: Sample;set-up.;8.;Gently rub the fresh/exposed area of the food items on the dry;starch-sprayed paper towel back and forth 10 - 15 times. Label where each;specimen was rubbed on the paper towel with a permanent marker (Figure 3).;9.;Provide a saliva sample by spitting in a separate bowl and rubbing;the paper towel in the saliva. Be sure not to spit on the paper towel directly;as you may unintentionally cross-contaminate your samples. Repeat this;step until you are able to adequately moisten the paper towel.;10.Wait five minutes.;11.Hold the IKI spray;bottle 25 - 30 cm away from the paper towel, and mist with the IKI solution.;12.The reaction will;be complete after approximately 60 seconds. Observe where color develops, and;consider what these results indicate. Record your results in Table 1.;Table 1;Substance vs. Starch Presence;Substance;Resulting Color;Presence of;Starch?;Positive;Control: Starch;Negative;Control: Student Must Select;Food;Product;Food;Product;Saliva;experiment 2;Effect of Temperature on Enzyme Activity;Figure 4:Catalase catalyzes the;decomposition of hydrogen peroxide to water and oxygen.;Yeast cells;contain catalase, an enzyme which helps convert hydrogen peroxide to water and;oxygen. This enzyme is very significant as hydrogen peroxide can be toxic to;cells if allowed to accumulate. The effect of catalase can be seen when yeast;is combined with hydrogen peroxide (Catalase: 2 H2O2?;2 H2O + O2).;In this lab you;will examine the effects of temperature on enzyme (catalase) activity based on;the amount of oxygen produced. Note, be sure to remain observant for;effervescence when analyzing your results.;Materials;(2) 250 mL Beakers;3 Balloons;30 mL 3% Hydrogen Peroxide, H2O2;Measuring Spoon;Permanent Marker;Ruler;20 cm String;3 Test Tubes (Glass);Test Tube Rack;Thermometer;Yeast Packet;*Hot Water Bath;*Stopwatch;*You Must Provide;Procedure;1.;Use a permanent marker to label test tubes 1, 2, and 3. Place them;in the test tube rack.;2.;Fill each tube with 10 mL hydrogen peroxide. Then, keep one of the;test tubes in the test tube rack, but transfer the two additional test tubes to;two separate 250 mL beakers.;3.;Find one of the balloons, and the piece of string. Wrap the string;around the uninflated balloon and measure the length of the string with the;ruler. Record the measurement 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. Use the 100 mL graduated cylinder to measure and pour approximately 200;mL of water into a small pot or microwave-safe bowl (you will have to measure;this volume in two separate allocations).;b.;If using a stovetop, obtain a small pot and proceed to;Step 4c. If using a microwave, 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 a medium 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 to;verify 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;without appropriate pot holders.;e.;If using a microwave, place the microwave-safe bowl in the;microwave and heat the water in 30 second increments until the temperature of;the water is approximately 100 ?C. Use the thermometer provided in your lab kit;to verify the water temperature. Wait approximately one minute before;proceeding to Step 5.;5.;Place Tube 1 in the refrigerator. Leave Tube 2 at room;temperature, and place Tube 3 in the hot water bath.;Important Note: The water should be at approximately 85 ?C when you place;Tube 3 in it. Verify the temperature with the thermometer to ensure the water;is not too hot! Temperatures which exceed approximately 85 ?C may;denature the hydrogen peroxide.;6.;Record the temperatures of each condition in Table 2. Be sure to;provide the thermometer with sufficient time in between each environment to;avoid obscuring the temperature readings.;7.;Let the tubes sit for 15 minutes.;8.;During the 15 minutes prepare the balloons with yeast by adding ?;tsp. of yeast each balloon. Make sure all the yeast gets settled to the bulb of;the balloon and not 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 when stretched 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 (the room temperature;test tube) making sure to not let the yeast spill into the test tube yet. Once;the balloon is securely attached to the test tube lift the balloon and allow;the yeast to enter the test tube. Tap the bulb of the balloon to ensure all the;yeast falls into the tube.;11.As quickly and;carefully as possible remove the Tube 1 (cold) from the refrigerator and repeat;steps 9 - 10 with Tube 1 using a balloon you prepared in step 8.;12.As quickly and;carefully as possible remove Tube 3 (hot) from the hot water bath and 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. Temperature;Tube;Temperature (?C);Balloon;Circumference (Uninflated, cm);Balloon Circumference;(Final, cm);1;- (Cold);2;- (RT);3;- (Hot);?;To;conduct your laboratory exercises, use the Laboratory Manuallocated under Course Content. Read the introduction;and the directions for each exercise/experiment carefully before completing the;exercises/experiments and answering the questions.;?;Save;your Lab4;AnswerSheet in the following format: LastName_Lab4 (e.g., Smith_Lab4).;?;You should submit your;documentas a Word (.doc or.docx) or;Rich Text Format (.rtf) file for;best compatibility.;Pre-Lab Questions;1.;How could;you test to see if an enzyme was completely saturated during an experiment?;2.;List three conditions;that would alter the activity of an enzyme. Be specific with your explanation.;3.;Take a look;around your house and identify household products that work by means of an;enzyme. Name the products, and indicate how you know they work with an enzyme.;Experiment 1: Enzymes In Food;Data Tables and Post-Lab;Assessment;Table;1: Substance vs. Starch Presence;Substance;Resulting Color;Presence of Starch?;Positive Control;Starch;Negative Control:Student Must Select;Food Product;Food Product;Saliva;Post-Lab Questions;1.;What were;your controls for this experiment? What did they demonstrate? Why was saliva;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? What experimental;evidence supports your claim?;4.;Saliva does;not contain amylase until babies are two months old. How could this affect an;infant?s digestive requirements?;5.;There is;another digestive enzyme (other than salivary amylase) that is secreted by the;salivary glands. Research to determine what this enzyme is called. What;substrate 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?t these;enzymes digest the stomach and small intestine, which are partially composed of;protein?;Experiment 2: Effect of Temperature on Enzyme Activity;Data Tables and Post-Lab;Assessment;Table;2: Balloon Circumference vs. Temperature;Tube;Temperature (?C);Balloon Circumference;(Uninflated, cm);Balloon Circumference;(Inflated, cm);1 - (Cold);2 - (RT);3 - (Hot);Post-Lab Questions;1.;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 dependent variable?;4.;How does the;temperature affect enzyme function? Use evidence from your data to support 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 graph to;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?


Paper#62826 | Written in 18-Jul-2015

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