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Enzyme Lab: Tropical Fruit and Gelatin

Background: Have you ever noticed the warning on a JELL-O package about pineapple?

Today you will learn the science behind that food warning. The enzymes in some tropical fruits can break down proteins. For example, papaya contains the digestive enzyme papain, which is often found as a component in meat tenderizers. Pineapple contains a digestive enzyme named bromelin. Enzymes can be affected by several factors such as pH and temperature. If the pH and temperature are altered beyond what the enzyme requires, the enzyme can start to denature or break down and change shape. Because an enzymes’ shape is so important for its function, once it denatures the enzyme can no longer function properly. Gelatin has long been a key ingredient for providing support for “jelled” deserts, salads, frozen drinks, and soft candies such as Gummy Bears. It contains a protein called collagen (a primary component of joints, cartilage, and nails), and various amino acids. Collagen is a protein, and like most proteins, when heated, it loses all of its structure. The polymer molecule unwinds. Then, when the denatured mass cools down, it soaks up all of the surrounding water like a sponge, forming gelatin.

Question: How does temperature and pH affect enzyme activity?

Enzyme Lab Part 1

Materials:

For each group For entire class

3 test tubes water

1 test tube rack pineapple juices (below)

4 (1 ml) disposable pipettes gelatin mixture

10ml graduated cylinder

Masking tape

Procedure:

1. Number and label the test tubes “1-3.”

2. Place 3 ml of the designated pineapple juice into each test tube. Use a separate pipette for each type of juice. Failure to do so may result in mixing of the juice types and inaccurate results.

o Tube 1: water only

o Tube 2: fresh pineapple juice

o Tube 3: Heated Canned pineapple juice

3. Add 10 ml of gelatin mixture to each test tube. Shake well to ensure proper mixing and place your samples in a cold water bath.

4. After a few minutes check the contents of each test tube for solidification of the contents and record your observations.

Enzyme Lab Part 2

Materials:

For each group For entire class

3 test tubes goggles

1 test tube rack apron

4 (1ml) disposable pipettes water

10 ml graduated cylinder pineapple juice

Masking tape 1M HCl

1M NaOH

Procedure:

1. Label 1 test tube “A” for acid, 1 test tube “B” for base, and the last test tube “C” for control.

2. Place 3 ml of fresh pineapple juice into each of the labeled test tubes. Transfer 1 ml of base, 1 ml acid, and 1 ml of water into the appropriate test tubes of pineapple juice. HINT: Use a different pipette for each test tube to avoid contamination.

3. Add 10 ml of gelatin mixture to each test tube. Mix well, being careful to not get any of the acid or base on your skin.

4. Place test tubes in ice water bathe

5. After a few minutes check each test tube for solidification or liquidity of the contents and record your observations.

Enzyme Pre-Lab

Directions: Read the background material provided to you. Using this material, your notes, and text, answer the following questions.

1. By definition, what is an enzyme? ____________________________________________________________ ________________________________________________________________________________________

2. (a) Describe what happens when a protein denatures. _____________________________________________ ________________________________________________________________________________________

(b) Is the denatured protein still able to function? ___________________________________________________

3. (a) What is the name of the enzyme we are using in this lab? ______________________________________

(b) What fruit is it found in? ________________________________________________________________

4. (a) What is the protein we are using in this lab? _________________________________________________

(b) For this lab, what is our food source for the protein? __________________________________________

5. In your own words, describe what happens to collagen when it is heated. ____________________________ ______________________________________________________________________________________

6. Read the procedure for Enzyme Lab part 1. Make a prediction regarding which of the three juices (water, fresh pineapple juice, or heated canned juice) will be solid and which will be liquid when you examine your results._________________________________________________________________________________

7. Why is water used as a “juice” in Enzyme Lab 1? _______________________________________________

8. Read the procedure for Enzyme Lab 2. Make a prediction as to which test tube’s contents (A, B, or C) will be solid.___________________________________________________________________________________

9. Why do you think this? ____________________________________________________________________ _______________________________________________________________________________________

10. Make a general hypothesis statement for the lab: What temperature, pH, and substance - water, fresh pineapple, or canned pineapple is best for solidification of the Jell-o (Denaturing the enzyme that breaks down collagen)_________________________________________________________________________________

__________________________________________________________________________________________________________________________________________________________________________________________

11. What is the independent variable? __________________ What is the dependent variable? _________________

12. What is the control? __________________What is kept constant?____________________________________

Enzyme Lab Data Sheet

|Group Member Name (Including you) |Duty/Job Description |

|1. | |

|2. | |

|3. | |

|4. | |

Enzyme Lab Part 1

|Test Tube |Juice |Temperature |State of test tube contents after cold water bath |

|1 |Water | | |

|2 |Fresh Pineapple Juice | | |

|3 |Heated Canned Pineapple Juice | | |

1. Was your hypothesis supported by the data? Why or why not? ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2. What caused some of the contents to stay liquid? _____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Enzyme Lab Part 2

|Test Tube |Contents |pH |State of test tube contents after cold water bath |

|A |Acid ( 1M HCL) | | |

|B |Base (1M NaOH) | | |

|C |Control (water) | | |

3. Was your hypothesis supported by the data? Why or why not? _____________________________________________________________________________________________________________________________________________________________

4. What caused some of the contents to stay liquid? _____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

5. How could the preparation processes in each of the types of pineapple change bromelin?

a. Fresh:___________________________________________________________________

b. Canned:_________________________________________________________________

6. For the types of pineapple that did not allow the gelatin to solidify, describe what you would need to do in order for that type of pineapple to allow the gelatin to solidify.______________________

____________________________________________________________________________________________________________________________________________________________________

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