Lab 4 1
Lab 4: Molecules of life This week, we are learning that the structural and functional differences between each of the 4 macromolecule groups (carbohydrates, proteins, lipids, nucleic acids) are very important in controlling the structure and function of biological systems such as cels. In this week’s lab, you will visualize first-hand how exposing the molecules of life to varying environments (temperature, pH, etc) dramatically impacts structure and function. Part 1: Heat and Macromolecule Structure and Function As we’re learning this week, denaturation occurs when the molecules of life are exposed to environmental conditions outside their normal range; however, the level and severity of denaturation may (and does) vary depending the specific macromolecule and the environmental conditions. This will be directly observed in our experiment below. In this experiment, we’ll be comparing Coke to Diet Coke. Specifically, regular Coke is sweetened with sugars (carbohydrates) such as monosaccharides glucose and fructose, and also the disaccharide sucrose (glucose+fructose), while Diet Coke is sweetened with a protein- based compound called aspartame (NutraSweet is the brand name; made by linking together two amino acids, aspartic acid and phenylalanine) which tastes sweet, but does not contain the caloric value of sugars. Materials
1 can/bottle Diet Coke
1 can/bottle Regular Coke
Access to heat: Microwave and Microwave safe cup or stovetop and saucepan. Experimental Set Up: A. Taste each, the Coke & Diet Coke. Record your observations regarding how each taste in the
table below. B. Carefully heat some Diet Coke and some regular Coke (separately). To do this, you can
• boil each on a stovetop for ~ 2-5 minutes, or • microwave some of each to boiling (make sure heat is sustained for 2-5 minutes).
C. Allow each to cool (it is ok to refrigerate or add ice). D. Taste each again*. Record your observations regarding how each tastes after heating in the
Coke Observations Regular Coke Diet Coke
After Heating (and cooling)
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*Note- while the solution(s) may taste different after heating, neither is more harmful to drink after heating than it was before heating. When you are finished, answer the following questions: 1. Briefly describe the taste of the regular Coke and the Diet Coke both before and after
heating. Did the taste of either change after heating, and how? 2. What do the results of the Coke/Diet Coke heating experiment tell you about the relative
denaturation sensitivity and process of carbohydrates versus proteins? Explain your answer.
3. Discuss how this Coke/Diet Coke heating experiment relates to the material that we learned this week. Use specific examples.
Part 2: Pineapple Jell-O For this activity, you’ll need some basic equipment outlined below. Plan ahead, making jello takes time (it needs to set in the fridge). You won’t be able to start this right before the lab is due 😉 Materials
Jell-O Gelatin, 2 identical packages (regular not sugar/fat free, not pudding, not premade; Gelatin must be listed as an ingredient), any flavor.
Fresh Pineapple (< 1/2 cup is all you will need)
Canned chunked pineapple in juice
Large bowl (or container) for mixing the finished Jell-O
4 smaller containers at least 3 inches tall (ideally clear, glass or plastic) (ex: juice glass)
Knife and cutting board
Tape and markers for making labels
Ruler (metric is best, 12 inch/30cm) Experimental Set Up: A. Label your 4 clear containers as follows
1: Fresh, 2: Fresh, 3: Canned, 4: Canned B. Prepare the gelatin by following the directions on the package. SAVE THE BOX. C. Pour equal amounts of liquid gelatin into each of the 4 numbered containers (see image). D. Place the gelatin into the refrigerator to set. Leave in the refrigerator until fruit is prepared. E. After the gelatin is fully set (it is now solid, jello), prepare the fruit. Remove all juice, and cut
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4 pieces of pineapple (2 Fresh and 2 Canned) each the size of a quarter. Make sure that the pineapple chunks are all approximately the same size and shape.
F. Remove all the gelatin containers from the refrigerator; from now on you will be working at room temperature.
G. Measure (in centimeters) the length of solid gelatin in each container (line ruler up alongside container) Record this measurement (at time 0; solid gelatin depth) in the table provided below (or on a separate piece of paper).
H. Place a piece of pineapple on the surface of the gelatin as appropriate (fresh pineapple to containers 1 and 2, canned pineapple to containers 3, and 4), and start the timer.
I. Every 15 minutes for the next 2 hours:
Examine/observe the appearance each gelatin + pineapple treatment.
Measure (in centimeters) the distance the fruit has moved into the gelatin
Record your measurements and describe your observations for each container in the table provided (or on a separate piece of paper).
J. Use this distance migrated to quantitatively evaluate each treatment.
For example, if you start with 8cm solid gelatin in your container and: after 1 hour the pineapple had moved through 5cm 62.5% (5/8cm*100) of the gelatin, and after 2 hour the pineapple had moved through 7cm 82.5% (7/8cm*100) of the gelatin.
Note: if desired, and pending clean handling of samples and measurement materials, the Jello+/-Pineapple treatments are safe to eat at this point. Make sure you record your observations before snacking! Experimental Fruit Depth Optional Data Collection Table:
Container 1: Fresh Container 2: Fresh Container 3: Canned Container 4: Canned
Distance Description Distance Description Distance Description Distance Description
solid gelatin depth
solid gelatin depth
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When you are finished, answer the following questions: 4. When you were setting up the gelatin+/-pineapple experiment, explain why was it better to
have two containers for each condition instead of only one?
5. Did the gelatin+/-pineapple experiment include a control? If so, what was it? If not, what could have served as a valid control for this experiment?
6. Briefly summarize the results of the gelatin+/-pineapple experiment. What were the effects of fresh versus canned pineapple on the gelatin? Include a description of each treatment, along with the relative % migration for each pineapple after 1 hour and 2 hours each.
7. Review the preparation instructions on the gelatin box. What do you notice about the
manufacturer’s recommendations regarding the addition of fruits to gelatin-based desserts? Why do you think this is? How does that relate to the gelatin+/-pineapple experiment?
8. Discuss your results for the gelatin+/-pineapple experiment treatments 1 and 2, versus treatments 3 and 4. What happened? What molecular component of the pineapple could be responsible for converting the gelatin from a solid to a liquid? Explain your rationale.
9. Using what you’ve learned this week about the structure and function of the molecules of
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life, discuss your results for the gelatin+/-pineapple treatments 3 and 4. What could be different between the canned and fresh pineapple (hint: during the canning process, pineapples are heated to a high temperature for sterilization purposes).
10. Note that in the instructions for the Jello and Pineapple experiment, the material specifically require Gelatin based Jello. The reason for this is because the experiment does not work with gels that are solidified with molecules other than gelatin (Dr. Pangle personally verified that premade “Snack Pack” pre-prepared gel cups, lacking gelatin, do not work with this experiment). What does this tell you about the chemical reaction that occurs between whatever was in the pineapple and it’s substrate? What was in the pineapple anyway?
11. Discuss how this gelatin+/-pineapple experiment relates to the material that we learned this
week. Use specific examples.
12. Let’s examine another example of macromolecules and structure and function. The composition of an egg white is 90% water and 10% protein (primarily a storage protein called Albumin that will be used to make all the proteins of the developing chick). Based on what you know about proteins, what happens to the albumin when you cook and egg, why?