UMUC Biology 102/103
Lab 4: Enzymes
INSTRUCTIONS:
On your own and without assistance, complete this Lab 4 Answer Sheet electronically and submit it via the Assignments Folder by the date listed in the Course Schedule (under Syllabus).
To conduct your laboratory exercises, use the Laboratory Manual located 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 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 Questions
1.How could you test to see if an enzyme was completely saturated during an experiment?
Answer ) Saturation means that all of the enzyme molecules are filled with substrate and adding more substrate will not increase the rate of reaction.
2.List three conditions that would alter the activity of an enzyme. Be specific with your explanation.
Answer )
Temperature- Increase in temp causes increase in enzyme activity
pH- Most enzymes work at pH-7
Substrate concentration- An increase in substrate concentration causes an increase in enzyme activity because there more collisions with the enzymes and therefore faster reaction.
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.
Answer )
Detergents:
Enzymes have been used in many kinds of detergents to degrade proteins causing stains.
Foods and Beverages :
Enzymes are used to produce foods like wine, beer, vinegar and cheeses. Biotechnology has made it possible to isolate and characterize the specific enzymes responsible for these processes.
Textiles :
Enzymes are widely used to prepare the fabrics for clothing and to enhance the preparation of cotton for weaving by reducing impurities while improving the quality of the final textile product.
Experiment 1: Enzymes in Food
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

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Procedure:
Remove the cap from the starch solution. Attach the spray lid to the starch solution.
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.
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).
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.
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.
Select two food items from your kitchen cabinet or refrigerator.
Obtain a kitchen knife and a cutting board. Carefully cut your selected food items to create a fresh surface.

Figure 3: Sample set-up.
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).
Wash your hands with soap and water.
Take your finger and place it on your tongue to transfer some saliva to your finger. Then, rub your moistened finger saliva into the paper towel. Repeat this step 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 also 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.
Wait five minutes.
Hold the IKI spray bottle 25 – 30 cm away from the paper towel, and mist with the IKI solution.
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 Dark Purple Yes
Negative Control : water yellow No
Food Product: Apple Yellow No
Food Product: Potato Dark Purple yes
Saliva: Amylase yellow No

Post Negative Control -Lab Questions
1.What were your controls for this experiment? What did they demonstrate? Why was saliva included in this experiment?
Answer )The positive control is starch while the negative control is water. The control of an experiment is the part of an experiment that does not change and serve as reference points. Saliva is included in this experiment to demonstrate the action of salivary amylase.
2.What is the function of amylase? What does amylase do to starch?
Answer )Amylase digest the starch so that no purple / black color is produced in the presence of amylase. It would break down the starch molecules, and lugol’s solution would not change color.
3.Which of the foods that you tested contained amylase? Which did not? What experimental evidence supports your claim?
Apple contained amylase and was able to break down starch, so when sprayed with lugol’s solution the towel did not turn purple. Potato does not have amylase, the towel where it was rubbed turned purple after spraying it with lugol’s solution.
4.Saliva does not contain amylase until babies are two months old. How could this affect an infant’s digestive requirements?
Answer )
Since amylase is needed for digesting starches or complex carbohydrates, this would result in these types of foods not being digested and possibly passed right through the system.
5.There is another digestive enzyme (other than salivary amylase) that is secreted by the salivary glands. Research to determine what this enzyme is call