· On your very own and also without assistance, finish this Lab 4 Answer Sheet electronically and submit it by means of the Assignments Folder by the day noted in the Course Schedule (under Syllabus).

You are watching: Experiment 1: enzymes in food

· To conduct your laboratory exercises, use the Laboratory Manual situated under Course Content. Read the advent and also the directions for each exercise/experiment carefully prior to completing the exercises/experiments and also answering the concerns.

· Save your Lab 4 Answer Sheet in the complying with format: LastName_Lab4 (e.g., Smith_Lab4).

· You have to submit your document as a Word (.doc or .docx) or Rich Text Style (.rtf) file for best compatibility.

Pre-Lab Questions

1. How might you test to check out if an enzyme was entirely saturated during an experiment?

2. List three conditions that would change the task of an enzyme. Be particular through your explacountry.

3. Take a look roughly your home and recognize household products that work-related by implies of an enzyme. Name the commodities, and also show exactly how you know they occupational via an enzyme.

Experiment 1: Enzymes in Food

This experiment tests for the visibility of amylase in food by utilizing 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 visibility of starch. As such, if the IKI solution transforms to a dark purple or babsence color during the experiment, one can identify that amylase is not current (because visibility of amylase would certainly break down the starch molecules, and the IKI would certainly not change color).



(1) 2 oz. Bottle (Empty)(1) 100 mL Graduated Cylinder30 mL Iodine-Potassium Iodide, IKIPermanent MarkerRuler2 Spray Lids30 mL Starch (liquid)*Cutting Board


*2 Food Products (e.g., ginger root, apple, potato, and so on.)*Kitchen Knife*Paper Towel*Saliva Sample *Tap Water

*You Must Provide


1. Rerelocate the cap from the starch solution. Attach the spray lid to the starch solution.

2. Rinse out the empty 2 ounce bottle through tap water. Use the 100 mL graduated cylinder to measure and also pour 30 mL of IKI right into the empty two ounce bottle. Attach the continuing to be spray lid to the bottle.

3. Set up a positive manage for this experiment by spraying a paper towel through 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 regulate for this experiment. Use your expertise of the clinical method and also speculative controls to establish this component (hint: what have to happen when IKI solution contacts somepoint that does not contain starch?) Identify your negative manage in Table 1.

Note: Be certain to area the positive and negative controls acomponent from each other to proccasion cross-contamicountry.

5. When the starch solution has actually dried, test your positive and negative controls. This action develops a baseline shade scale for you to evaluate the starch concentration of the food products you will certainly test in Steps 7 - 11. Record your outcomes in Table 1.

6. Select 2 food items from your kitchen cabinet or refrigerator.

7. Obtain a kitchen knife and a cutting board. Carefully reduced your schosen food items to develop a fresh surface.

Figure 3: Sample set-up.

Figure 3: Sample set-up.

8. Gently rub the fresh/exposed location of the food items on the dry, starch-sprayed paper towel back and forth 10 - 15 times. Label wright here each specimales was rubbed on the paper towel via a permanent marker (Figure 3).

9. Wash your hands with soap and water.

10. Take your finger and location it on your tongue to move some saliva to your finger. Then, rub your moistened finger saliva right into the paper towel. Repeat this action till you are able to adequately moisten the paper towel.Note: You have to constantly wash your hands before emotional your tongue! Conversely, if you do not wish to put your hands in your mouth, you might also administer 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 straight as you might unintentionally cross-contaminate your samples.

11. Wait 5 minutes.

12. Hold the IKI spray bottle 25 - 30 cm ameans from the paper towel, and also mist with the IKI solution.

13. The reactivity will certainly be finish after around 60 seconds. Observe where shade develops, and take into consideration what these outcomes show. Record your outcomes in Table 1.

Table 1: Substance vs. Starch Presence


Resulting Color

Presence of Starch?

Positive Control: Starch

Dark Purple 


Negative Control : Cellulose

Brownish red color


Food Product: Apple

Dark Purple  


Food Product: Potato

Dark Purple  


Saliva: Amylase

Brownish red color


Blog post Negative Control -Lab Questions

1. What were your controls for this experiment? What did they demonstrate? Why was saliva had in this experiment?

2. What is the attribute of amylase? What does amylase execute to starch?

3. Which of the foods that you tested consisted of amylase? Which did not? What speculative proof supports your claim?

4. Saliva does not contain amylase till babies are 2 months old. How can this influence an infant’s digestive requirements?

5. There is another digestive enzyme (other than salivary amylase) that is secreted by the salivary glands. Research to identify what this enzyme is dubbed. What substprice does it act on? Wright here in the body does it become caused, and why?

6. Digestive enzymes in the gut incorporate proteases, which digest proteins. Why don’t these enzymes digest the stomach and also little intestine, which are partly created of protein?

Experiment 2: Effect of Temperature on Enzyme Activity

Yeastern cells contain catalase, an enzyme which helps convert hydrogen peroxide to water

Figure 4: Catalase catalyzes the decomposition of hydrogen peroxide to water and also oxygen.

Figure 4: Catalase catalyzes the decomplace of hydrogen peroxide to water and oxygen.

and also oxygen. This enzyme is extremely substantial as hydrogen peroxide can be toxic to cells if enabled to accumulate. The result of catalase can be viewed as soon as yeast is combined with hydrogen peroxide (Catalase: 2 H2O2 → 2 H2O + O2).

In this lab you will certainly study the impacts of temperature on enzyme (catalase) activity based on the amount of oxygen developed. Keep in mind, be sure to remajor observant for effervescence as soon as analyzing your results.


(2) 250 mL Beakers3 Balloons30 mL 3% Hydrogen Peroxide, H2O2 Measuring SpoonPermanent MarkerRuler20 cm String


3 Test Tubes (Glass)Test Tube RackThermometerYeastern Packet*Hot Water Bath*Stopwatch*You Must Provide


1. Use a irreversible marker to label test tubes 1, 2, and also 3. Place them in the test tube rack.

2. Fill each tube via 10 mL hydrogen peroxide. Then, store one of the test tubes in the test tube rack, but move the 2 added test tubes to 2 separate 250 mL beakers.

3. Find one of the balloons, and also the item of string. Wrap the string approximately the uninflated balloon and meacertain the size of the string via the ruler. Record the measurement in Table 2.

4. Create a warm water bath by perdeveloping the following steps:

a. Determine if you will certainly use a stoveheight or microwave to heat the water. Use the 100 mL graduated cylinder to meacertain and also pour roughly 200 mL of water right into a small pot or microwave-safe bowl (you will certainly need to measure this volume in 2 sepaprice allocations).

b. If utilizing a stovetop, attain a little pot and also continue to Tip 4c. If making use of a microwave, acquire a microwave-safe bowl and also continue to Step 4e.

c. If utilizing a stove, place a tiny pot on the oven and rotate the oven on to a tool warmth establishing.

d. Carecompletely monitor the water in the pot until it involves a soft boil (roughly 100 °C). Use the thermometer offered in your lab kit to verify the water temperature. Turn the range off when the water starts to boil. Immediately continue to Tip 5.CAUTION: Be certain to revolve the range off after producing the hot water bath. Monitor the heating water at all times, and also never manage a warm pan without proper pot holders.

e. If making use of a microwave, place the microwave-safe bowl in the microwave and warmth the water in 30 second increments until the temperature of the water is around 100 °C. Use the thermometer gave in your lab kit to verify the water temperature. Wait approximately one minute before proceeding to Tip 5.

5. Place Tube 1 in the refrigerator. Leave Tube 2 at room temperature, and also place Tube 3 in the warm water bath.

Important Note: The water must be at around 85 °C as soon as you location Tube 3 in it. Verify the temperature through the thermometer to ensure the water is not also hot! Temperatures which exceed roughly 85  °C might denature the hydrogen peroxide.

6. Record the temperatures of each problem in Table 2. Be sure to provide the thermometer through enough time in between each setting to avoid obscuring the temperature readings.

7. Let the tubes sit for 15 minutes.

8. Throughout the 15 minutes prepare the balloons via yeast by including ¼ tsp. of yeastern each balloon. Make sure all the yeast gets settcaused the bulb of the balloon and not caught in the neck. Be certain not spill yeast while taking care of the balloons.

9. Carecompletely stretch the neck of the balloon to help encertain it does not rip when stretched over the opening of the test tube.

10. Attach the neck of a balloon you prepared in action 8 to the optimal of Tube 2 (the room temperature test tube) making certain to not let the yeast spill into the test tube yet. Once the balloon is secudepend attached to the test tube lift the balloon and also permit the yeastern to enter the test tube. Tap the bulb of the balloon to encertain all the yeast falls into the tube.

11. As easily and also carefully as possible remove the Tube 1 (cold) from the refrigerator and also repeat procedures 9 - 10 through Tube 1 making use of a balloon you ready in action 8.

12. As conveniently and closely as possible rerelocate Tube 3 (hot) from the hot water bath and repeat procedures 9 - 10 via Tube 3 utilizing a balloon you prepared in action 8.

13. Swirl each tube to mix, and also wait 30 secs.

14. Wrap the string around the center of each balloon to meacertain the circumference. Measure the size of string through a leader. Record your dimensions in Table 2.

Table 2: Balloon Circumference vs. Temperature


Temperature (°C)

Balloon Circumference (Uninflated; cm)

Balloon Circumference (Final; 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 impact enzyme function? Use evidence from your data to assistance your answer.

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5. Draw a graph of balloon diameter vs. temperature. What is the correlation?

6. Is tright here an unfavorable control in this experiment? If yes, recognize the regulate. If no, imply how you could revise the experiment to include an adverse manage.

7. In general, just how would certainly a boost in substprice transform enzyme activity? Draw a graph to show this connection.

8. Deauthorize an experiment to recognize the optimal temperature for enzyme function, finish with controls. Wbelow would certainly you discover the enzymes for this experiment? What substrate would you use?