Identifying Macromolecules 10/2016

PURPOSE

  • To test for the presence of macromolecules in various foods.
  • Identify the unknown macromolecule composition of oatmeal, milk and yogurt

BACKGROUND

The most common macromolecules (organic compounds) found in living organisms are lipids, carbohydrates, proteins, and nucleic acids. Common foods, which often consist of plant materials or substances derived from animals, are also combinations of these macromolecules. Scientists use certain tests to identify the presence of macromolecules.When molecules are studied, they are often visualized indirectly. Through the use of indicators, specific molecules can be detected. Indicators are chemicals that change color when another molecule is present

INTRODUCTION

You’re a scientist at the Food and Drug Administration’s Center for Nutrient Analysis and you have the job to analyze food for the concentrations and presence of various biological molecules. Scientists have asked for your assistance in helping to kill off a new organism that is a threat to our very existence.! We understand that these organisms’ cells start to get sick and die when fed substances with high levels of complex carbohydrates and protein. Scientists have also found that the invaders seem to thrive and grow rapidly when fed simple sugars. Simple carbohydrates are simple sugars with a chemical structure that is composed of one or two sugars and breakdown very quickly in the body. Complex carbohydrates are made up of three or more sugars, which are usually linked together to form a chain. Due to their complexity, they take a little longer to digest, than simple carbohydrates. Sometimes these complex carbs are called dietary fiber.

Your team is taking a break from the regular task of food label analysis in order to determine which of three substances – yogurt, milk or oatmeal – will be the best food to feed to the invading organismsin hopes of killing them off. It is up to you and your team to save Earth!

MATERIALS:

Culture tubes

Culture tube Rack

Tube Clamp

Transfer Pipet

Benedicts Solution

Distilled Water

Biuret Reagent

Iodine Solution

GelatinApple juiceMilkPotato solution

Oatmeal

Yogurt

Procedure Part I: Using the Standard solutions please perform these tests:

Protein --- Biuret Test

  1. Use a transfer pipet to transfer 1mL of each food item into the culture tubes. (One food item in per culture tube.)
  2. Add 6 drops of Sodium Hydroxide (NaOH) to each culture tube
  3. Add 3 drops of Copper Sulfate (CUSO4 )to each culture tube
  4. Gently shake the contents of each culture tube.
  5. Biuret Reagent changes color from blue to violet in the presence of protein. In the Data Table, write a “+” if protein is present or a “-“ if protein is not present. Share your test results with the rest of your lab group

Simple Carbohydrate---Benedict’s Test

  1. Use a transfer pipet to transfer 1mL of each food item into the culture tubes. (One food item in per culture tube.)
  2. Add 10 drops of Benedict’s Solution to each culture tube.
  3. Gently shake the contents of each culture tube.
  4. Place the culture tubes in the BOILINGhot water bath for 3-5 minutes. Watch for a color change.
  5. Remove the culture tubes using culture tube holders.
  6. A rusty brown color in response to Benedict’s Solution indicates a large amount of simple sugars. An orange color indicates a moderate amount and a green or yellow color indicates a small amount of sugar.
  7. A blue color indicates no sugar present (negative result)
  8. In the Data Table, write a “+” if simple carbohydrates are present or a “-“if simple carbohydrates are not present. Share your test results

Complex Carbohydrate Iodine Test

  1. Use a transfer pipet to transfer 1 mL of each food item into the culture tubes. (one food item in per culture tube.)
  2. Add 3 drops of Iodine to each culture tube.
  3. Gently shake the contents of each culture tube.
  4. Iodine causes complex carbohydrates to turn dark blue or black. Substances without starch are colored brown by the iodine, but do not react with it and the solution will look yellowish brown.
  5. In the Data Table, write a “+” if complex carbohydrates are present or a “-“ if complex carbohydrates are not present. Share your test results with the rest of your lab group

Procedure Part II: Testing Foods for Unknown Macromolecule Composition

  1. Obtain samples of Oatmeal, Milk and Yogurt and perform the above test on each. Record your results.

Name ______Period____

Identifying Macromolecules

Pre-Lab Questions: Answer the following questions using complete sentences prior to starting the lab

  1. What are the three macromolecules that we will be testing for in this lab?
  2. What macromolecule will you NOT be testing in today’s lab?
  3. What is the purpose of using distilled water as one of your test substances?
  4. Explain in detail what the purpose of an indicator is?

Data TableBiuretBenedict’s Iodine

Standards (controls)
(Known Composition) / Protein / Simple Carbohydrate / Complex Carbohydrate
Distilled Water
Gelatin Solution
Apple Juice
Potato Solution
Unknown Composition / Protein / Simple Carbohydrate / Complex Carbohydrate
Milk
Yogurt
Oatmeal

Analysis & Conclusions: Answer the following questions on your lined paperusing complete sentences.(That I can read) Be thorough in yourresponses, use lab data as evidence to support your answers.

  1. Look at your data table and list which macromolecules were present in each of the unknowns? Milk, Yogurt, Oatmeal
  2. Using Iodine, what color changesindicatethe presence of a complex carbohydrate?
  3. Using Benedict’s Solutionwhat color changesindicate presence of a simple carbohydrate?
  4. Using Biuret Reagent, what color changesindicate the presence of a protein?
  5. Describe at least two errors you may have made while completing this lab.
  6. Explain how the above errors may have impacted your results.
  7. You are getting prepared to take a “Man vs. Wild” hike. Using your data and your understanding of nutrition, which of the unknown substances would provide the best fuel for your body to endure this long adventure?Explain in detail why you choose that food
  8. Do the sugars in the apple juice need to be broken down by your digestive system before they can be utilized as an energy source for your body? Explain.
  9. Why do you think did we had to heat the benedicts indicator to have it work?
  10. What foods would you suggest a person with diabetes should eat if they should avoid simple carbs?
  11. Explain why complex carbs are better for the body than simple carbohydrates.
  12. What conclusion could you make if a positive test for any of the macromolecules occurred in the culture tube containing only distilled water?
  13. Two students are arguing because one says that the invading organism should be feed milk and the other one says they should be feed oatmeal.
  14. Who is Right?
  15. Explain why one is better than the other.