Name _____________________
Period___ Date_____
Organic Compounds
Macromolecules
Purpose:
We are what we eat. All living things, including humans, are made out of organic compounds. In
this investigation you will test different substances and determine what types of macromolecules
are found in each type of food.
Introduction:
Nutrients are substances or compounds that supply your body with energy and form the building
blocks of life, we call them macromolecules. The food you eat contains nutrition important to your
body. Sugars and starches make up a group of organic compounds called carbohydrates, which are
important in supplying our body with energy. Organic compounds called proteins are important
for growth and repair. Lipids are organic compounds that can supply up to four times the amount
of energy as carbohydrates or proteins.
You can perform qualitative tests to identify the presence of organic compounds in foods using
indicators, chemical substances that react in a certain way when a certain substance is present.
Benedict’s Solution used to identify the presence of reducing sugars such as glucose. Lugol’s iodine
solution is used to identify the presence of starch. Biuret solution is used to identify the presence of
proteins. Newspaper is used to identify the presence of lipids.
Nutrients:
Carbohydrates, which include sugars and starch, are digested into glucose, which is transported
through the blood stream and stored in the liver as glycogen. Carbohydrate digestion begins in the
mouth and continues in the small intestines.
Proteins are digested into peptides then to amino acids (the building blocks of proteins). The
majority of protein digestion occurs in the stomach and small intestines.
Lipids are broken down into fatty acids. The majority of lipid digestion occurs in the small
intestines.
NOTE: Water is not a nutrient or source of calories. However, it is critical to the digestive process.
Colorimetric Test is one in which color change is used to assess whether a reaction has occurred. In
this lab, you will use colorimetric tests to determine the presence of carbohydrates and proteins.
Topic I: Carbohydrates:
Iodine Test for Starch: If starch is present then the solution will turn from yellow to blue/black in
the presence of iodine (I2KI).
Benedicts Test For Sugar: If sugar is present then the solution will turn from blue to green,
orange, or brown in the presence of Benedict’s solution.
Starch + Iodine  blue/black color
Sugar + Benedict’s solution  green/orange/brown
Part A: Testing for Carbohydrates (Starch):
Group
Substance Added
Water
1
2
3
4
5
6
7
8
Apple Juice
Egg White
Potato
Pizza
Sprite
Chips
Cereal
Pasta
Table A
Reagent and color of
reagent
Color observed after test
Part B: Testing for Carbohydrates (Sugar):
Appearance After Test:
Amount of sugar:
Color
Group
0
(none)
+
(trace)
++
(little)
+++
(some)
++++
(much)
Blue
Blue-green
Green
Yellow
Orange/red
Substance Added
Table B
Reagent and color of
reagent
Color observed after test
Water
1
2
3
4
5
6
7
8
Apple Juice
Egg White
Potato
Pizza
Sprite
Chips
Cereal
Pasta
Question:
List two places in the body where carbohydrate digestion occurs.
_____________________________
Which food substance(s) contains the most starch?_________________________________________
Which food substance(s) contains the most sugar?_________________________________________
Topic II: Proteins:
If proteins are present, the solution will turn pink (some protein) to purple (much protein) when
Biuret solution is added.
Part C: Testing for Proteins:
Group
Substance Added
Table C
Reagent and color of
reagent
Water
1
2
3
4
5
6
7
8
Apple Juice
Egg White
Potato
Pizza
Sprite
Chips
Cereal
Pasta
Question:
List two places in the body where proteins digestion occurs.
_________________________________
Which food substance(s) contains the most
protein?________________________________________
Which food substance(s) contains no
protein?_____________________________________________
Color observed after test
Topic III: Lipids:
Part D: Testing for Lipids:
Group
Substance Added
Table D
Reagent and color of
reagent
Color observed after test
Water
Oil
1
2
3
4
5
6
7
8
Apple Juice
Egg White
Potato
Pizza
Sprite
Chips
Cereal
Pasta
Questions:
Name one place in the body where lipid digestion takes place. ________________________________
Which food substance(s) contain the most lipids?
__________________________________________
Which food substance(s) contain the most lipids?
__________________________________________
CONCLUSION:
Write a conclusion for this lab activity. This must be in paragraph form! Use the questions from
the lab and the following questions to guide you:
What are macromolecules? What are the different categories or groups?
What is a colorimetric test?
How did you test for each organic compound?
Why do we use one test tube with only water?
Explain the results for the substances that you tested.