Materials Included In Kit

Additional Materials Required

Prelab Preparation

If a comparison between the effects of detergent versus fresh pineapple or kiwi juice on gelatin is desired (see Lab Extensions), prepare the juice fresh beforehand using the following method:

1. Remove the outer rind of the pineapple and/or cut up the fruit into chunks.
2. Use a food processor or large mortar and pestle to squeeze out the juice.
3. Filter the juice through cheesecloth or a strainer to remove the pulp.
4. Store extra juice in a tightly closed container and refrigerate or dispose of down the drain with the water running.

Safety Precautions

All of the materials used in this activity are considered non-hazardous. Use caution when using hot plates and stirring hot solutions. Wearing safety goggles is strongly recommended. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory. Please consult Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Place solid gelatin into waste cans according to Flinn Suggested Disposal Method #26a. All liquids and small amounts of gelatin used in this activity may be disposed of down the drain with volumes of water according to Flinn Suggested Disposal Method #26b. Save extra detergent mixtures and label the containers. Rinse and save paper clips, cups and pipets for future use.

Lab Hints

• Enough materials are provided in this kit for 30 students working in pairs, or for 15 groups of students. This laboratory activity could be completed in two 50-minute class periods depending on the cooperation and skill level of the students. The Prelaboratory Activity should be completed before beginning the lab. Collecting and graphing of the data can be done on the final day of the lab.
• While students are collecting data at their workstations, draw a table on a chalkboard, whiteboard or on a poster board for groups to record their data. The class data table needs only three columns: Detergent/Substance Used, Amount of Liquid Present after 24 hours and pH—Initial/pH—Final.
• The amount of liquid in mL for the type of disposable pipet included in the kit is listed (see Flinn Catalog for diagrams of other types):

Graduated pipet—25 drops = 0.7 mL. If and when you may need to use other types of pipets besides the ones provided in the kit, be sure and instruct students as to how many drops of water and detergent to add inside the paper clips to ensure volume consistency.

• Adding gelatin to vigorously boiling water will cause it to bubble over.

Teacher Tips

• A major focus of the lab is to have students recognize that detergents containing enzymes will generally hydrolyze gelatin (protein) better than detergents without enzymes.

• Encourage student to bring in samples of the laundry detergents used at home, if different than the included samples. If the actual container is not brought in, students should write down the ingredients and bring the list with them.
• This activity is a great opportunity to relate biology to the real world. Send students on a hunt to find enzymes in familiar products at the local market. Household cleaners, contact lens cleaners, meat tenderizers and perhaps some personal care items are good places to start looking.
• The most common classes of enzymes and their use in detergents are outlined:

  Proteases: Remove stubborn protein stains (e.g., blood, grass) and will perform at temperatures as low as 5 °C.

  Amylases: Remove residues of starchy foods (e.g., mashed potatoes, baby food, ready-cooked meals and gravy).

  Cellulases: Offer the benefits of color brightening, whitening, softening and fabric care. These enzymes are capable of removing fuzz and pills from cotton fabrics, making them look new for a longer time.

  Lipases: Remove stains, such as lipstick, frying fats, butter, salad oil, sauces and perspiration stains around cuffs and collars.

Further Extensions

A number of other variables may be tested in this lab activity, such as the following:

• Assign a group to decrease the gelatin’s pH by adding 5 mL of vinegar.
• Assign a group to add fresh pineapple or kiwi juice instead of detergent.
• Assign a group to add the juice from canned pineapple instead of detergent.
• Assign a group to use sugared or sugar-free gelatin. If this option is used, sugared gelatin requires 18 g/50 mL of water; sugar-free requires 1.8 g/50 mL.
• Assign a group to make and use a 10% solution of meat tenderizer.
• Assign a group to make and use a detergent solution concentration greater than 10% or less than 10%.
• Assign a group to keep their cups in the refrigerator or on ice during the same 24 hours.

Answers to Prelab Questions

On a separate sheet of paper, use the information found the Background section to help answer the questions and complete the following statement.

1. What do you think enzymes are called that digest or break down proteins?

Proteases

2. When a protein is denatured, describe in general terms what happens to it? Why might that be a problem?

The structure of the protein is destroyed. When a protein’s structure is destroyed, it can no longer function the way it should.

3. Write out and complete this statement:

If the primary ingredient in gelatin is a (choose one) carbohydrate, fat, protein and drops of detergent are put on the surface of gelatin, then ... (Predict the results of the interaction.)

Example: If the primary ingredient in gelatin is protein and drops of detergent are added to the top of the gelatin and left for 24 hours, then the gelatin will liquefy if the detergent contains protease enzymes, which break apart the amino acid chains.

Sample Data

Answers to Questions

1. Why were only drops of water added to one of the cups?

The water acted as a control to ensure that room temperature or other factors were not responsible for the liquid in the cup after 24 hours.

2. 1. Based on the results, what is the primary ingredient in gelatin?

      Protein

   2. If the primary ingredient listed in 2a was not what you said, how might the lab results been different?

      If gelatin was not mostly protein, the detergent enzymes, which digest protein, would not create so much liquid in the experiment cup.

3. 1. Was the group’s prediction correct? (Refer to Prelab Question 3.)

      Student answers will vary.

   2. How do the results compare to the prediction?

      Student answers will vary.

4. From the class data, which detergent(s) affected the gelatin the most?

Student answers will vary.

5. From the class data, which detergent(s) affected the gelatin the least?

Student answers will vary.

6. Do the group’s results differ from the class results? Briefly explain.

Student answers will vary but may include: Yes, because it’s a smaller data set than the class data.

7. Compare the ingredients of the detergents that affected the gelatin the most. Are there any ingredients that are common to each of them? If yes, list them.

Student answers will vary.

8. Was there an ingredient that the most effective detergent(s) did not list??

a. If yes, which one(s)?

Enzymes—the most likely answer.

b. How do you explain the effectiveness of that/those detergent(s) in the absence of that ingredient?

Enzymes are probably in the detergent, they are just not listed as ingredients.

9. (Optional) Compare your group’s results to a group that changed one of the variables in the experiment: pH, temperature of the gelatin, added substance other than detergent, changed the detergent’s concentration.

a. How does the final pH and Amount of Liquid after 24 hours differ?

Student answers will vary.

b. Propose two logical explanations for the differences.

Student answers will vary.

In summary:

10. Which type of organic substance in gelatin must also be found on or in “dirty” clothes? Support your answer using data from the experiment!

Protein, student answers will vary according to data.

11. Name one factor discovered in this experiment that appears to affect the ability of enzymes to “do their job.” Support your answer with data.

High or low pH, temperature, student answers will vary according to data.

12. 1. Where do the enzymes used in many of today’s detergents come from?

       Bacterial “factories”

    2. Why are these organisms able to produce these enzymes?

       They have been genetically engineered to do so.

13. List three sources of error that did, or could have, affected the results.

• Drops of detergent were not counted correctly, adding too much or too little detergent to the gelatin.
• The room temperature may have been too warm, melting some of the gelatin. Therefore, the liquid in the cup after 24 hours may not have all been a result of enzyme action.
• Inaccurately measuring the detergent to make the 10% solutions may have resulted in concentration > or <10%.

References

The Science Teacher, Vol. 59, pp. 46–49, NSTA, Arlington, VA, 1992.

http://www.msichicago.org (accessed May 2018)

http://www.accessexcellence.org (accessed May 2018)

http://www.novozymes.com (accessed May 2018)

Introduction

Modifying an organism’s genetic structure to create a genetically modified organism (GMO) has been controversial since the process was developed. However, thanks to genetically modified bacteria, clothes today are getting much cleaner than they have ever been. Many laundry soaps have now been supplied with a secret “weapon,” the same “weapon” used by fresh pineapple and kiwi juice to prevent dissolved gelatin from becoming solid. (There is even a printed warning about it on packages of Jell-O^®!) In this experiment, you will learn something about gelatin and detergents that you probably never knew!

Concepts

• Genetic engineering

• Proteolytic enzymes
• Enzymes
• Chemical reactions—hydrolysis

Background

Proteins are the basic building blocks of all living things. Without proteins, no living thing would exist. The breaking apart (digestion) of proteins, called proteolysis, begins with separating the covalent bonds that link amino acid chains together to form large protein molecules. Globular proteins, called enzymes, are responsible for this process. Enzymes are generally named after the compounds upon which they act. These compounds are called substrates. For example, enzymes that digest lipids (fats) are called lipases; the enzyme that breaks down sucrose (table sugar) is sucrase.

Through a process known as genetic engineering, certain strains of bacteria have been converted into microscopic factories to produce enzymes they would not usually make. In addition, these enzymes are altered to be more stable and more effective in environmental conditions which might otherwise denature “ordinary” enzymes. Some of these conditions, which include extremes in temperature and pH, are very common inside washing machines. When these “modified” enzymes are collected from their bacterial “factories” and added to detergents, our clothes get cleaner. Why? The dirt on or in clothes—sweat, grass stains, mustard, ketchup, lipstick—contain compounds, such as pigments, which are made from protein, lipids, and/or carbohydrates. Many of these substances do not wash out with just water.

Gelatin, the main ingredient in Jell-O^®, is formed when fibrous proteins, such as tendons, are denatured. When proteins are denatured, they lose the structure that makes them able to function in a specific way. For example, when raw chicken is boiled in water, the muscle (meat) falls off the bones. This happens because the complex structure of the tendons, which connect muscles to bones, is destroyed by the heat. As the liquid cools, the amino acids chains which formed the tendon’s original structure are still present but that complex structure cannot be reformed. The resulting semi-solid fluid is what we call gelatin. Jell-O is simply purified gelatin with sugar, flavoring and coloring (pigment) added.

Experiment Overview

The purpose of this lab is to draw conclusions about the cleaning effectiveness of a detergent containing bacterially derived enzymes versus a detergent that does not list enzymes as an ingredient.

Materials

Prelab Questions

On a separate sheet of paper, use the information found the Background section to help answer the questions and complete the following statement.

1. What do you think enzymes are called that digest or break down proteins?
2. When a protein is denatured, describe in general terms what happens to it? Why might that be a problem?
3. Write out and complete this statement:

If the primary ingredient in gelatin is a: (choose one) carbohydrate, fat, protein and drops of detergent are added to the top of the gelatin, and left for 24 hours, then... (Predict the results of the interaction.)

4. Use the provided data table to record all lab data or make your own on the answer sheet.

Safety Precautions

All of the materials used in this activity are considered non-hazardous. Follow normal lab safety procedures when using hot plates and stirring hot solutions. Wear chemical splash goggles. Wash hands thoroughly with soap and water before leaving the laboratory.

Procedure

Day 1

1. Pour 50 mL of water into a 150-mL beaker. Bring the water almost to boiling on a hot plate. Note: When small, steady streams of bubbles begin to rise, the water is hot enough.
2. Mass 2 g of gelatin and while stirring, add the gelatin and a drop of food coloring to the hot water.
3. Determine the initial pH of the solution and record it in the data table.
4. Label one polypropylene cup with a Name, Period and the word Control. Pour 20 mL of the dissolved gelatin solution into it. Cover with plastic wrap or Parafilm to slow down evaporation. Set aside to cool.
5. Label the second polypropylene cup with Name, Period and the word Experiment. Pour 20 mL of the gelatin solution into it. Cover with plastic wrap or Parafilm to slow down evaporation. Place next to the other cup to cool. Note: If your group has been assigned to decrease the gelatin’s pH by adding vinegar to the liquid gelatin, do so at this time. Determine the experimental solution’s new pH and record in the data table.
6. Select a detergent for testing, locate the ingredient label on the package, and write down all the listed ingredients in the Ingredients column of the data table.
7. Rinse and dry the beaker used to make the gelatin before leaving class.

Day 2

1. Make a 10% solution of the detergent selected on Day 1 by mixing 1 g or 1 mL to 9 mL of tap water in a clean polypropylene cup.
2. Remove the covering from the cups made on Day 1 and gently lay a small paper clip on the surface of the gelatin in the middle of each cup.
3. Using a disposable pipet, add 25 drops of water to the inside of the paper clip in the Control cup. (Do not be concerned if the water runs out from underneath the paper clip.)
4. Add 25 drops of detergent solution to the inside of the paper clip in the Experiment cup. Record the amount of water and detergent added (in mL) in the data table. Note: If using powdered detergent, undissolved powder will remain at the bottom of the mixing cup. Add only the dissolved detergent to the inside of the paper clip.
5. Cover both cups again and place them inside a cabinet or drawer for another 24 hours. The room’s temperature should be no warmer than 22 °C (72 °F).
6. Rinse out and dry the cup used to mix the detergent solution before leaving class.

Day 3

1. Obtain a 10-mL graduated cylinder.
2. Remove the covering from each cup and carefully observe. Write a brief description of your observations in the data table. Is there liquid on the top of solid gelatin? Where is the paper clip in relation to the liquid?
3. Carefully pour any liquid that is in each cup into a 10-mL graduated cylinder.
4. Record the amount of liquid, the pH and the type of detergent or other substance used in the group and class data tables.
5. Consult your instructor for proper disposal procedures.

Student Worksheet PDF

10667_Student1.pdf