Class Set Do Not Write
CLASS SET DO NOT WRITE!!!!
Organic Molecules Mini-Lab
Background: Organic molecules are molecules that contain carbon. Living systems are made up of organic molecules. The 4 main classes of organic molecules are carbohydrates, lipids, proteins, and nucleic acids. In this lab we will test various substances for the presence of complex carbohydrates (starch) and proteins.
Test 1:
Carbohydrates can be divided into three groups, monosaccharides, disaccharides, and polysaccharides. Mono and disaccharides are simple sugars. Polysaccharides are complex carbohydrates such as starch. In this part of the lab we will be testing for the presence of starch, a complex carbohydrate. Lugol’s iodine solution will turn a dark purple/black color in the presence of starch.
Procedures: (First make your Predictions)
1. Place a very small amount of each substance listed into one of your plastic beakers. (A little goes a long way)!
2. Record original color in Table 1.
3. Add 2 drops of Lugol’s solution on top of each sample.
- Lugol’s solution is liquid iodine
4. Mix contents by gently swirling if necessary.
5. Record color in Table 1 of results
Substances:
- Water
- Milk
- Bread
- Table Sugar
- Potato
- Chicken Broth
***MAKE SURE YOU RINSE EACH BEAKER BETWEEN TESTS! ***
Test 2:
Proteins are large polymers made up of many amino acid monomers. Proteins are the workers of life. They perform various tasks inside living things. Proteins also make up muscle tissue, as well as hair and fingernails. In this part of the lab we will be testing for the presence of proteins in various substances using Biuret reagent. Biuret reagent turns from a blue color to a violet/purple when in the presence of proteins.
Procedures: (First make your Predictions)
1. Place a small amount of the same substances listed in Test 1 in each plastic beaker.
2. Record original color
3. Add 5-10 drops of Biuret solution on top of each sample.
4. Mix contents by gently swirling if necessary.
5. Record Color Changes in Table 1
Results:
Table 1: Lugol’s Test for Starch
Test Tube
/ Prediction (+/-) / Final Color / Results (+/-)1. Water
2. Milk
3. Bread
4. Table Sugar
5. Potato
6. Chicken Broth
Table 2: Biuret’s Test for Protein
Test Tube
/ Prediction (+/-) / Final Color / Results (+/-)1. Water
2. Milk
3. Bread
4. Table Sugar
5. Potato
6. Chicken Broth
Conclusion: Answer the following questions in complete sentences.
1. What is a starch, and how is it different from table sugar? ( ______saccharide should be in your answer)
2. What were we using to test for starch, and how could you tell if it was positive or negative?
3. Based on what you have learned and your background knowledge, what types of foods generally contain starches?
4. What is the monomer of a carbohydrate?
5. What are 4 functions of carbohydrates?
6. What were we using to test for proteins? How could you tell if it was positive?
7. What is the monomer of a protein?
8. Describe how the shape of a protein relates to its function (job).
9. What are 5 functions of proteins?
10. What 2 classes of organic compounds did we not test for in today’s lab? Write 1 function of each as well.