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Do not write on this – return to Mrs.
Cardellini when you turn in your lab
McMush Food Test – Biology Honors
INTRODUCTION: All living things are composed of the same 4 basic organic
compounds: carbohydrates (simple sugars and starches), proteins, lipids (fats, oils, waxes,
and steroids), and nucleic acids (DNA and RNA). Many of these compounds, along with
vitamins and other nutrients, provide your body with the energy needed to carry out life’s
activities. These compounds are present in the plants and animals you use as food. To
determine the presence of these substances, scientists use chemicals called indicators which react with the
compound to produce a color change. The change is a result of the chemical reactions between the indicator and the
specific molecular arrangement (structure) of the compound being tested. In this lab, you will test for specific
compounds in food from McDonalds by using various indicators. If a color change is observed, the test is said to
have a positive result, confirming the presence of a particular compound.
Carbohydrates
You know these as sugars and starches. Monosaccharides or simple sugars such as glucose and fructose (C6H12O6)
function as an energy source in cells and are also used to build cell structures and other organic molecules within the
cells. Disaccharides are composed of two monosaccharides joined together. Sucrose (table sugar) is a disaccharide
composed of one glucose and one fructose molecule. Polysaccharides: These are long chains of monosaccharides
bonded together. Plants store excess glucose in the form of starch, a polysaccharide composed of long chains of
glucose. Starches can be found in potatoes, rice, wheat, corn, bananas, peas, beans, lentils, and other tubers, seeds
and fruits of plants. Animals (and humans) store excess glucose in the form of glycogen in the liver and muscles.
Between meals the liver breaks down glycogen to glucose and releases it into the blood stream to supply glucose to
cells in need. Other important polysaccharides are cellulose and chitin. Cellulose makes up the cell wall of plants
whereas chitin provides structure to fungi and the exoskeleton of arthropods.
Lipids
A lot of lipids function as long-term energy storage. One gram of fat stores more than twice as much energy as one
gram of carbohydrates. Lipids are also an important component of the cell membrane in phospholipids. The fatty
acid tails are hydrophobic (water repelling) while the phosphates are hydrophilic (water loving). Lipids consist of
glycerol and fatty acid "tails". The fatty acid chains can be saturated, with all carbons saturated with hydrogen atoms
forming a straight chain without double bonds. Unsaturated fatty acids contain double bonds within the carbon
chain, which results in a bend of the chain.
Proteins
Proteins are complex, specialized molecules composed of carbon, oxygen, hydrogen, nitrogen and sometimes sulfur.
The building blocks of proteins are amino acids. There are 20 different amino acids that combine to form
polypeptides (proteins). Proteins have many important roles in organisms. Structural proteins such as collagen or
elastin, provide support. Regulatory proteins such as enzymes control cell processes. Proteins also play an important
part in the immune system (antibodies), oxygen transport (hemoglobin), movement (muscles) etc.
PURPOSE: To determine the organic compounds present in a McDonald’s meal.
OBJECTIVES:
 name the four biological macromolecules and their building blocks
 test food samples for the presence of lipids, proteins, and simple and complex sugars
MATERIALS: McDonald’s food
12 Epitubes
Benedicts’ solution (sugar)
Lugol’s iodine solution (starch)
forceps
blender
hot plate
Biuret solution (protein)
Sudan III or IV (lipids)
foam holder
pipettes
beakers
colored pencils
***Goggles are to be worn during this lab at all times****
Methods:
Part 1:
Testing Known Solutions (Control Tests)
1. Mark four epitubes with a “+”, mark four epitubes with a “-“ and four with “E.”
2. LIPIDS TEST: Place 10 drops of the “+oil” solution into your tube marked +L for the positive control. Place 10
drops of water into a tube (marked –L) for your negative control. Add 2 drops of Sudan solution into
each test tube, and observe the color then record in the chart. DO NOT SHAKE. Continue with PART 2,
LIPIDS.
3. PROTEIN TEST: Place 10 drops of the “+protein” solution into your tube marked +P for positive. Place 10
drops of water into a tube (-P) for your negative control. Add 8 drops of the Biuret solution to each test,
shake well, and observe the color and record in the chart. Continue with PART 2, PROTEINS.
4. GLUCOSE TEST: Place 10 drops of the “+ Monosaccharide” solution into your PYREX tube marked +G for
positive control. Place 10 drops of water into a tube (-G)for your negative control. Add 4 drops of
Benedict’s solution in the tubes. Prepare the McMush tube as described below. Place all 3 tubes into the
foam holder then place gently into a beaker of water that is boiling. Ask Ms. Bolton for help if the holder is
already in the boiling water. Boil for 2-3 minutes (or until you see a color change) and remove with the
forceps, observe the color, and record in the chart.
5. STARCH TEST: Place 10 drops of the “+starch” solution into your tube marked +S for positive control.
Place 10 drops of water into a tube (-S) for your negative control. Add 3 drops of Lugol’s iodine solution
into each test tube, shake, and observe the color; record in the chart. Continue with PART 2, STARCH.
Part 2:
Testing the McMush Meal: (Experimental Test)
1. LIPIDS (fats) TEST: Place 10 drops of the “McMush” solution one tube marked EL.
Add 2 drops of Sudan solution into the tube, and observe the color then record in the chart.
2. PROTEIN TEST: Place 10 drops of the “McMush” solution one tube marked EP.
Add 8 drops of the Biuret solution to the tube, shake as instructed, and observe the color and record
in the chart.
3. GLUCOSE TEST: Place 10 drops of the “McMush” solution one PYREX tube marked EG.
Add 4 drops of Benedict’s solution into the epitube. Place the test tube into the foam holder in the
boiling water using the tweezers. Boil for 2-3 minutes (or until you notice any color change) and remove
with the forceps, observe the color and record in the chart.
4. STARCH TEST: Place 10 drops of the “McMush” solution one tube marked ES.
Add 3 drops of Lugol’s iodine solution into the test tube, shake as instructed, and observe the color then
record in the chart.
When finished, all epitubes should be washed thoroughly and turned upside down in your rack. Have Mrs.
Cardellini check your station so that you can be dismissed.
DATA CHART: (be sure to give this chart an appropriate title)
Food Substances
Fats
Protein
Glucose
Starch
You determine how to arrange the rest of your data
with both the control and experimental tests. There
won’t be quantitative data this time.
DISCUSSION:
1. What was the purpose of the water in the first test? Why are controls important?
2. What is meant by the term ‘positive result’?
3. If you had an unknown solution that gave the following results, what can you conclude about the compounds
present?
Iodine – blue/black
Benedicts – blue Sudan IV –red ring
Biurets – light blue
4. State Standards 1H states you must know macromolecules (polysaccharides, proteins, nucleic acids, and lipids) in
cells are synthesized from a small collection of simple precursors. List the precursors (monomers) for each of the
four organic compounds. You may do this in chart form if you wish.
CONCLUSION: Visit http://nutritiondata.self.com/ and enter your information on the DAILY NEEDS calculator
(on bottom right). 1. How many calories do you burn in a day (look at est. energy requirement? 2. Scroll down to
the very bottom where it shows you your recommended macronutrients. List these requirements. Think about what
you ate yesterday – does it appear that you are eating your requirements? Explain. 3. Now visit your favorite fast
food website (websites are also on my biology class weblinks) and create a full meal (entrée or sandwich, side and
drink). Write out the meal you composed and its calorie and fat content. 4. How does the calorie and nutritional
content relate to the amount of calories you burn in a day? What might happen if you continue these same eating
habits as you grow older?
+ Protein
+ Monosacc.
+ Polysacc.
+ Lipid