Enzyme Salad Lab:
NOTES TO THE TEACHER:
We usually do this lab when we are discussing digestive enzymes and temperature dependence of enzymes. The students like the application of biochemistry to something they eat.
Here are some suggestions that have helped make the lab more smoothly.
Preparing the gelatin: Stir two envelopes of KNOX unflavored gelatin into 800 ml of hot water. This should be plenty for three classes. Store it in a warm water bath when the students are using it so it will pour easily.
Remind the students to rinse of the razor blade between types of pineapple. Clean up is easier if they cut the fruit on paper plates.
Canned Pineapple: Use the chunky style.
Fresh Pineapple: You will probably have to buy a whole pineapple and most of it will be left after the labs. You and the students might enjoy eating it.
Ice baths made in beakers or cans will eliminate too much movement through the room.
The name of the digestive enzyme you were working with is bromelin. It is named after the group of plants to which the pineapple belongs - the Bromeliads.
ENZYME SALAD LAB
by: Sue Balala
Have you ever noticed the warning on a JELL-O package not to use fresh or frozen pineapple? Today we are going to put the fruit into gelatin and see what happens. What are some possible results?
BACKGROUND: The enzymes in some tropical fruits can break down protein. For example meat tenderizers have the enzyme, papain, that breaks down some of the fiber. We use it to soften up a tough piece of meat. The papain comes from the papaya fruit. Pineapple has a digestive enzyme called bromelin.
MATERIALS:
Four Test Tubes
Fresh Pineapple
Hot Gelatin
Canned Pineapple
Ice Water Bath
Frozen Pineapple
Glass Marker
Single-edged Razor Blade
Test Tube Rack
PROCEDURE:
l. With the razor blade carefully cut equal sized pieces of fresh, canned, and frozen pineapple. The pieces should be just small enough to slide into your tubes.
2. Label the test tubes l-4.
3. Pour 3 ml of liquid gelatin into each of the four tubes.
4. Place the different pieces of pineapple into the first three tubes. Notice that test tube #4 contains only gelatin.
5. Mix the contents of the tubes by rolling them upright betweenthe palms of your hands.
6. Place all four test tubes into the ice water bath.
7. Every few minutes check to see if the gelatin is setting in the tubes. When test tube#4 has gelled firmly you can remove all the tubes and compare the consistencies
8. Record you observations in the table below.
TUBE CONTENTS:
1. Gelatin and Fresh Pineapple
2. Gelatin and Canned Pineapple
3. Gelatin and Frozen
4. Gelatin
Create your Data Table to Record your Data:
DISCUSSION QUESTIONS:
1. Why did test tube #4 contain only gelatin?
2. What could account for the different results in the tubes?
3. How could the canning process change bromelin?
4. What could you do to fresh pineapple that would allow the salad to gel?
5. Design an experiment to find a temperature at which a meat tenderizer works the best?
Enzyme Action:
MATERIALS NEEDED:
- Spot plate or glass slide
- Marker
- Toothpick for mixing
- Forceps
- Milk-whole, skim or 1%
- Droppers
- Liquid Lactaid
- Glucose test paper
- Any Glucose solution
- Any Sucrose solution
BACKGROUND:
Most foods that are ingested are composed of large, complex molecules. These molecules are not useful to the body unless they are first broken down into small ion. Digestion is dependent on various enzymes produced by the organs of the digestive system to make the chemical activity of hydrolysis occur in a reasonable amount of time.
- Define:
- hydrolysis
- substrate
- active site
- How many sugar rings are there in lactose? Based on this classify lactose.
- Complete the following:
- C12H22O11 Lactose or milk sugar
- Add water
- +______
- C12H24H12
- Subtract glucose formula
- +______
Galactose formula
- What would be the enzyme that activates this reaction?
- Where does this enzyme act in your body?
- Where is this enzyme produced in your body?
- Name the substrate .
DIGESTING LACTOSE WITH LACTASE
- Use the marker to draw and number 4 circles on glass plate or slide. Use different droppers for each solution and add the following:
Circle 1: add 2 drops of glucose solution
Circle 2: add 2 drops of milk
Circle 3: add 1 drop of Lactase
Circle 4: add 1 drop of Lactase plus 2 drops of milk (mix with toothpick)
- After 3 minutes, test each of the above for the presence of glucose by dipping a piece of glucose test paper to each.
- After 2 minutes, note any color change in the glucose test paper.
- Record the data in table 1 and complete the table.
TABLE 1 RESULTS OF TEST FOR GLUCOSE
Circles / Color Before / Color After / Interpretation (+/-)1. Glucose
2. Milk
3. Lactase
4. Lactase + Milk
- In which circle would you expect the hydrolysis of the milk sugar, lactose?
- What products would result after this hydrolysis?
How did you know this? - Why did you test the glucose with the glucose test paper?
Why did you test the lactase with the glucose test paper? - Does milk contain glucose?
What is your proof? - Does milk combined with lactase contain glucose?
What is your proof? - Some people cannot drink milk because their digestive systems do not produce lactase. If milk is ingested, it cannot be digested. This results in cramping, bloating, gas, and diarrhea. Suggest a treatment that would allow a person such as this to ingest milk.