Activity 1: Determine the Presence of Organic Compounds

Activity 1: Testing for the Presence of Organic Compounds

Biochemists study the chemical composition of living things. They analyze the complex chemical combinations and reactions involved in metabolism, reproduction, and growth. Biochemists do most of their work in biotechnology, which involves understanding the complex chemistry of life. These chemists may perform tests to identify organic compounds; compounds that consist of carbon and hydrogen. Carbohydrates, lipids, proteins and nucleic acids (DNA and RNA) are all organic compounds. Each of these macromolecules plays an important role in your body. Carbohydrates such as starches can be broken down into smaller units to give your body energy. Lipids such as fat serve as long-term storage of energy and for cushioning vital organs while nucleic acids store genetic material. Some proteins provide an organism’s structure while others digest macromolecules. Indicators are chemicals that change color when they react with a specific compound. Benedict's solution is used to identify the presence of simple sugars and will turn yellowish orange when heated. Lugol's iodine solution is used to identify the presence of starch and will turn bluish black. Biuret solution is used to identify the presence of protein and will turn purple. A brown paper bag can be used to observe the presence of fats. The paper will absorb the water whereas oil cannot be absorbed and an oily spot will be evident. In this lab you will test for the presence of organic compounds in various solutions. You will test for starch, sugar, proteins and lipids. Before each experiment you must formulate a hypothesis based on what you have learned about macromolecules and color change indicators.

Materials:  6 test tubes per group  Test tube rack  Lab soaker or paper towels  Brown paper bag cut into squares  Benedict’s solution  Lugol’s iodine  Biuret solution  Sharpie pens  Gloves  Lab coat or apron  1 mL transfer pipettes  Potato starch  Gelatin  Glucose solution  Vegetable oil  Parafilm wax paper  Clock or timer  Graduated cylinder  Water bath with submerged test tube rack or beakers filled with water

Procedure: 1. Wear protective eyewear, gloves and apron or lab coat 2. Create a “placemat” with a lab soaker or paper towels a. Keep all of your equipment and solutions on your mat

3. Using a Sharpie, label each test tube with your initials for identification

4. Label each tube appropriately for each experiment a. Experiment 1: one tube labeled for starch one tube labeled water b. Experiment 2: one tube labeled for glucose one tube labeled water c. Experiment 3: one tube labeled for albumin one tube labeled for water

5. Place test tubes in a test tube holder

6. Mix appropriate indicator with solutions according to experiment a. Experiment 1: add a few drops of iodine to each test tube i. Place a small square of Para film wax over each test tube ii. Mix gently iii. Observe and record any color changes from the original color of the indicator b. Experiment 2: using a transfer pipette, add 1mL Benedict’s solution to each tube i. Heat at 100 Co for 2-3 minutes in a hot water bath ii. Observe and record any color change from the original color of the indicator c. Experiment 3: using a transfer pipette, add 1mL Biuret’s solution to each tube i. Place a small square of Para film wax over each test tube ii. Mix gently iii. Observe an record any color change from the original color of the indicator d. Experiment 4: i. Label a piece of brown paper with your initials ii. Draw 2 circles about the size of a quarter on your paper iii. Put 2 drops of vegetable oil in one circle and 2 drops of water in the other iv. Allow to dry at room temperature v. If oil is present, it will leave a spot on the paper vi. Observe and record your data

CLEAN UP 1. Using a sink, rinse out test tubes and put them back into test tube holders to dry 2. It is safe to throw the used transfer pipettes into the garbage 3. Throw away the brown paper, your gloves and your “placemat” 4. Put away your protective wear NAME ______DATE ______

DATA TABLES

EXPERIMENT 1: TEST FOR STARCH WITH IODINE

HYPOTHESIS ______

Color Tube Indicator Solution Treatment Change? Starch Present? A few drops of Add a few 1 1mL starch Iodine drops of Lugol’s iodine A few drops of 2 1mL water and observe Iodine

EXPERIMENT 2: TEST FOR SUGAR WITH BENEDICT’S SOLUTION

HYPOTHESIS ______

Color Sugar Tube Indicator Solution Treatment Change? Present? 1 1mL Benedict’s 1mL glucose Mix and heat test tubes for 2 minutes 2 1mL Benedict’s 1mL water in a 100oC water bath and observe EXPERIMENT 3: TEST FOR PROTEINS WITH BIURET’S REAGENT

HYPOTHESIS ______

Tube Indicator Solution Treatment Color Protein Present? Change? 1 1mL Biuret’s 1mL gelatin Mix and 2 1mL Biuret’s 1mL water observe

EXPERIMENT 4: TEST FOR LIPIDS WITH BROWN PAPER

HYPOTHESIS ______

Solution Treatment Fat Present? 2 Drops oil Allow circles to dry and observe 2 Drops of Water

Analysis Questions 1. What did the color changes indicate for experiments 1 through 3? Explain. 1.

2. How do you know that fat was present using the brown paper test? Explain.

3. Was your hypothesis accepted or refuted for experiment one? Use your data to explain.

4. Was your hypothesis accepted or refuted for experiment two? Use your data to explain.

5. Was your hypothesis accepted or refuted for experiment three? Use your data to explain.

6. Was your hypothesis accepted or refuted for experiment four? Use your data to explain.

7. Identify the controls in each experiment: 1.)