Macromolecules in Food Lab
Introduction: Biological macromolecules are defined as large molecules made up of smaller
organic molecules. There are four classes of macromolecules: carbohydrates, lipids, proteins and
nucleic acids. Carbohydrates consist of two major groups, sugars and starches, and are a great
source of energy. Lipids are hydrophobic molecules which also store energy and consist of fats, waxes, and oils. All living
things make and depend upon proteins, which are made up of repeating amino acid units. DNA and RNA are both
nucleic acids, used for storing and communicating genetic information.
Test #1 – Biuret Indicator:
1) CAUTION: Biuret solution can burn skin. Be sure to wipe off and wash off any spills with plenty of water.
2) Fill 8 wells of your well plate half full with the Biuret indicator.
3) The remainder of the 8 wells should be filled with the liquid solutions you will be testing.
4) Observe and record the observations in your data table using either a + or a – sign .
5) **Positive test will be purple; a negative test will be blue**
6) Clean out your well plate by rinsing it off at the sink.
Test #2 – “Grease Spot” Test:
1 drop
1 drop
1 drop
1 drop
1 drop
1 drop
1 drop
1) Obtain a long strip of a brown paper bag. Make sure it is not doubled up.
2) Use a pen to label where you will place one drop of each liquid solution.
3) Using the pipet, place one large drop of the liquid solution over the appropriate word. DO NOT MIX PIPETS!
4) Let the solutions sit for one minute.
5) Take the paper bag and hold it up to the light or window.
6) Observe and record the observations in your data table using either a + or a – sign .
7) **Positive test will be a translucent (see through) “grease spot”**
Test # 3 – Iodine Indicator:
1) CAUTION: Iodine can burn skin. Be sure to wipe off and wash off any spills with plenty of water.
2) Fill 8 wells of your well plate half full with the Iodine indicator.
3) The remainder of the 8 wells should be filled with the liquid solutions you will be testing.
4) Observe and record the observations in your data table using either a + or a – sign .
5) **Positive test will be a very dark purple/black; a negative test will be brownish orange**
6) Clean out your well plate by rinsing it off at the sink.
Name ________________________________________ Date __________________ Period ______
Macromolecules in Food Lab
Purpose: To investigate three of the biological macromolecules by testing for the presence of starches (carbohydrate),
proteins, and lipids in foods. This will be done using three separate tests, but YOU will be responsible for determining
what macromolecule each substance is testing for.
1. Hypothesis: Which of the eight substances do you think will test positive for PROTEIN?
2. Hypothesis: Which of the eight substances do you think will test positive for LIPIDS?
3. Hypothesis: Which of the eight substances do you think will test positive for CARBOHYDRATES?
4. Complete the following data table. Put a + or –
Food Item
Biuret Indicator
1) Water
2) Protein Powder
Solution
3) Potato Solution
4) Vegetable Oil
5) Corn Starch
Solution
6) Apple Juice
7) Egg White
Solution
8) Glycerin
Food Lab Analysis Questions:
5. Define the term macromolecule.
6. What are the four biological macromolecules?
Grease Spot Test
Iodine Indicator
7. According to your results, Biuret solution is an indicator for which macromolecule (Carbohydrates, Proteins or
Lipids)?
8. According to your data, the “grease spot” test indicates the presence of which macromolecule (Carbohydrates,
Proteins or Lipids)?
9. According to your data, Iodine is an indicator for what macromolecule (Carbohydrates, Proteins or Lipids)?
10. Fill in the following chart
Macromolecule
Function
Monomer
(Building Block)
Examples
Starch
Cellulose
Potatoes
Pasta
Amino Acids
Insulation
Provide short term
energy in the body
Insoluble in water
Nucleic Acids
Enzyme Lab
INTRODUCTION: What would happen to your cells if they made a poisonous
chemical? You might think that they would die. Interestingly, your cells are always
making poisonous chemicals. They do not die because your cells use enzymes to
break down these poisonous chemicals into harmless substances. Enzymes are
proteins that speed up the rate of reactions that would otherwise happen more
slowly. The enzyme is not altered by the reaction. You have hundreds of different enzymes in each of your
cells.
Each of these enzymes is responsible for one particular reaction that occurs in the cell. In this lab, you will
study an enzyme that is found in the cells of many living tissues. The name of the enzyme is catalase (KAT-uhLAYSS); it speeds up a reaction which breaks down hydrogen peroxide, a toxic chemical, into 2 harmless
substances--water and oxygen.
The equation for this reaction is as follows:
2H2O2  2H2O + O2
This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a byproduct of many
normal cellular reactions. If the cells did not break down the hydrogen peroxide, they would be poisoned and
die. In this lab, you will study the catalase found in liver cells. You will be using chicken liver. It might seem
strange to use dead cells to study the function of enzymes. This is possible because when a cell dies, the
enzymes remain intact and active for several weeks, as long as the tissue is kept refrigerated.
Catalase Reaction Procedure
1. Place 2 ml (one full pipet) of the 3% hydrogen peroxide solution into a clean test tube.
2. Add raw liver to the top of the test tube.
3. Using the probe, gently push the liver into the hydrogen peroxide solution. Observe the reaction.
4. Throughout this investigation you will describe the rate of the reaction (how rapidly the solution
bubbles) by giving each reaction a “rating” using a scale of 0-5.
(0=no reaction, 1=slow, little bubbles, 5= very fast, many bubbles).
5. Record any additional observations in the “observations” column of your data table. Information
might include temperature change(!), color change, no change, etc.
6. Repeat steps 1-3 using the three other substances (cooked liver, potato, yeast). Record the rate of
reaction for the four substances in the data table
Name ___________________________________________________ Date ________________ Class ________________
Enzyme Lab
2H2O2  2H2O + O2
Purpose: To observe the effects of enzymes in living organisms and to see the effect of heat on an enzyme.
1. Complete the following data table. See the instructions for the rate of reaction guideline.
Substance
Rate of Reaction (0-5)
Observations
Chicken liver (raw)
Chicken liver (cooked)
Yeast
Potato
Enzyme Analysis Questions
2. Draw and label an energy diagram which illustrates a reaction taking place both with and without an enzyme.
3. When raw liver was added to the test tube it should have caused a temperature change for the hydrogen
peroxide. Describe the temperature change. Was this reaction endothermic or exothermic?
4. What GAS is produced when hydrogen peroxide reacts with raw liver? Hint: use the chemical equation!
5. By adding hydrogen peroxide, we are testing for the presence of the enzyme catalase. The formation of bubbles
indicates a positive result. Based on your data, which samples contained the enzyme catalase?
6. According to the results, which tissue tested contained the most amount of Catalase?
7. According to the results, which tissue tested contained the least amount of Catalase?
8. Hydrogen peroxide and raw liver resulted in a very strong reaction. Hydrogen peroxide and cooked liver had no
reaction. Knowing that substrates are acted upon only by enzymes with a specific shape (“Lock and Key”
Model), what do the raw liver vs. cooked liver results imply about the enzyme Catalase?
9. Catalase in an enzyme. Enzymes are an example of which macromolecule (Carbohydrates, Proteins, Lipids,
Nucleic Acids)?
10. What would happen if your body was unable to produce the enzyme Lactase?