THERE'S ALWAYS ROOM FOR JELL-O©
This lesson was developed by Elaine Kilmer and myself while working with the curriculum project "Science in the Real World: Microbes in Action" sponsored by the Coordinating Board for Higher Education, the University of Misouri-St. Louis and the Mathematics and Science Education Center.
Type of activity:
Set up in one class period and completed in the next.
Preparation of Materials:
JELL-O© Plates: Mix 36 g of regular JELL-O© dissolved in 100 ml boiling water.
Use sodium carbonate (Na2CO3) to adjust the pH to 8 (optimum for enzyme activity). (Armour, S. and Fall, R. 1992, BioTechniques: Enzymes Made Easy. "The Science Teacher" vol.59. #8, pps. 46-49)
Pour 25 ml per petri plate for each student or team of 2 students. Refrigerate.
Select some detergents that include enzymes in the ingredient list and some that don't list enzymes. Mix 10% solutions with distilled water and put in test tubes with a dropping pipette in each tube. Caution students NOT to mix up the droppers because that will mix the solutions. Students will use 6 different solutions. Have more than 6 different solutions available and allow students to select the ones that they want. Using 3 replicate tubes of 10 different detergent solutions will provide enough tubes for a class.
JELL-O© contains the protein gelatin that gels as it cools. Gelatin is a protein that is the gelling component of JELL-O©. Enzymes called proteases digest (break bonds in) the protein chain so that the broken protein chains can no longer gel. JELL-O© liquefies when exposed to these enzymes. Many detergents and cleaners have added enzymes that break down or digest a variety of organic molecules, one of which is gelatin.
In this activity, "There's Always Room For JELL-O©", students cut wells in JELL-O© and load the wells with different detergent solutions. With this simple digest, they observe that many, but not all detergents contain an active ingredient that breaks down JELL-O©. This ingredient is an enzyme which is specific for the breakdown of proteins, of which gelatin is just one example.
Gelatin, an important ingredient in JELL-O©, is a protein obtained from animal tissue. It is this substance that causes the JELL-O© to solidify when cooled.
The purpose of this activity is to observe the effect of some common detergents on JELL-O©.
- 1 petri dish containing JELL-O©
- 1 marking pen
- 1 plastic straw section
- 1 metric ruler
- 1 toothpick
- Access to a variety of detergent solutions each with its own pipette
- Access to distilled water with a pipette included for the control well
1. Obtain a JELL-O© filled petri dish. Identify the dish on the bottom by writing (near the edge and in small letters) your name, class hour, and today's date.
2. Place the dish right-side up on the template provided and remove the lid. Using the plastic soda straw section, cut wells in the plate using the template as a pattern.
3. Remove the plugs of JELL-O© with a toothpick. Take care not to tear the layer of JELL-O©. Number the wells on the bottom of your dish as shown on the template.
4. Measure the diameter of the wells (in mm) by placing the dish on a metric ruler. Record on Table 1 as "initial diameter".
5. Choose 6 different detergent solutions and record the names on Table 1.
6. Use only the dropper that is in each solution. Do not mix droppers from tube to tube. Carefully "load" each of the wells with these detergents. To load the wells, place the pipette into the well and gently dispense just enough liquid to fill the well. Load distilled water into well #7. This will be your negative control.
Be sure the numbered well corresponds with the number of the detergent listed on your data sheet.
Do not drop any liquid onto the surface of the JELL-O©! This can ruin the results of this experiment. If you do - note the location of the drop by drawing a picture in your notebook.
7. Replace the lid on the petri dish. Do not turn the dish upside down. You will spill the solutions that you just loaded into the wells.
8. Let the dish sit for several hours or overnight in a cool place. Do not disturb the dish during that time.
1. Observe the wells in the petri dish. Record any physical change in the JELL-O© that you see around some or all of the wells.
2. Was there any change in the JELL-O© around well #7? Explain.
3. Measure the diameter of each well in mm. The diameter of a well is the distance from solid JELL-O© on one side to the solid JELL-O© on the other side. Record this measurement on Table 1 as the "final diameter."
Well# Detergent Diameter Diameter
1 mm mm
2 mm mm
3 mm mm
4 mm mm
5 mm mm
6 mm mm
7 distilled water mm mm
4. Which products increased the size of the well diameter?
5. Based on your observations, what ingredient in JELL-O© do you think was changed? (Hint: refer to the BACKGROUND)
When we eat JELL-O©, gelatin is digested by enzymes produced by organs of our digestive system. All organisms produce enzymes that can break down large molecules such as proteins, fats, and carbohydrates. Look at the ingredients listed for each of the products and try to determine what chemicals did the best job of digesting gelatin.
6. What ingredient in these products is probably responsible for the breakdown of the protein, gelatin?
Enzymes are chemicals that are produced by all living things. They are organic molecules belonging to the group of compounds known as proteins.
7. Suggest an explanation of how enzymes, which are made by living organisms, can be found in detergents and cleaners.
Enzymes are highly specific. This means that they only cause a certain chemical or group of chemicals to react. They do this by recognizing the shape of a chemical or the similar structure of a group of chemicals. Thus, some enzymes only act on one specific chemical, while others may act on a group of chemicals that all share a common basic structure. An example of this would be a general protease which may act on many different proteins by always breaking down the same type of bond in each. The result is either the breakdown or the formation of a product. Enzymes names often end in "ase". For example, lactase is the enzyme that breaks down the sugar, lactose.
8. Suggest a name for the enzyme that breaks down the protein, gelatin.
9. Why would it be advantageous for manufacturers to have enzymes added to their detergent products?
FOR FURTHER STUDY
1. Design and carry out an experiment that would test the effect of different temperatures on the activity of the enzyme additives to detergents.
2. Design and carry out an experiment that would test the effect of different pH environments on the activity of the enzyme additives to detergents.
3. Design and carry out an experiment that would test other types of cleaning products' activity on the protein gelatin.