Name __________________________________________________ Per. _____ Date __________
Lab- Chemicals of Life
Introduction:
Learn the chemical tests for the major macromolecules found in cells and then use them to test
for the presence of the chemicals in unknown samples.
Biological Concepts:
 Macromolecules
o Carbohydrates
 Starches
 Monosaccharide
o Proteins
o Lipids
o Nucleic acids
 Biochemistry
Chemical nature of living cells
Background
The fundamental chemical components of cells can be grouped into four basic categories:
 Carbohydrates-monosaccharide, polysaccharide
 Proteins
 Lipids
 Nucleic acids
Other chemicals, such as water, salts and minerals are also present and vital to living cells.
Tests have been devised by biologists for determining the presence of many key chemicals.
In this activity four key tests will be used to determine the nature of 5 unknown solutions.
Materials
Unknown A
Iodine indicator
Unknown B
Biuret indicator
Hot water bath
Unknown C
Sudan IV indicator
Beral-ype pipets
Unknown D
Benedicts indicator
Labels
Unknown E
4 Microcentrifuge tubes
Marker
Observation Note
Definitions:
Indicator - a substance, when added to an unknown, will cause a color change.
Unknown- a substance that you are trying to determine its composition.
Solution- is the indicator mixed with the unknown.
Indicators:
Iodine mixed with a polysaccharide will turn the solution from a yellowish brown to a dark purple.
Benedicts mixed with a monosaccharide will turn blue to brown red
Biuret mixed with a protein will turn the solution from a light blue to a purple.
Sudan IV mixed with a lipid will create 2 layers in the solution. The top layer containing lipid will be rusty
red
Procedure
Each group will perform test one of the unknowns for each macromolecule of Life (ie.- Group 1 will
only test unknown A for polysaccharides lipids, proteins, monosaccharide, Group 2 will test
unknown B)
1.) You will be assigned to one of the unknowns
2.) Grab 4 microcentrifuge tubes
3.) Label unknown letter and microcentrifuge CP (for carbohydrates, polysaccharide ) Label
another microcentrifuge P (for proteins,) label another L (for lipids,) and label the last
microcentrifuge CM (for carbohydrate monosaccharide) Each group will have 4
microcentrifuges
4.) Add 12 drops of unknown into each microcentrifuge
5.) Use required amount of indicator into each microcentrifuge and see if a color change shows.
6.) If color change is showing put a + (showing the molecule is present in the unknown)
7.) If no color change shows put a – (showing the molecule is NOT present in the unknown)
Unknown ______
Polysaccharide Test
Use Iodine indicator
(use 2-4 drops)
Protein Test
Use Buirets
Indicator
(Use 5-10 drops)
Lipid Test
Use Sudan IV
indicator
(use 10 drops)
Monosaccharide
Test
Use Benedict’s
indicator (Use 14
drops) Place in hot
bath for 10 minutes
Microcentrifuge CP
Microcentrifuge P
Microcentrifuge L
Microcentrifuge CM
Starting
color of
indicators
Ending color
(+ or -)
REVIEW: While waiting for the monosaccharide in hot bath, answer the following questions from the
book.
1. What are monomers of carbohydrates (simple sugars)?
2. What are polymers of carbohydrates (complex large molecules of sugars?)
3. What are the monomers or the building blocks of proteins? Polymers?
4. What is a monomer of a lipid? Polymer?
5. What is the difference between a saturated and an unsaturated fat?
6. We didn’t test for nucleic acids, but what are 2 kinds of nucleic acids, and what are their
monomers?
Class Information
Testing Unknowns Table
Unknown
A
B
C
D
E
Starch
Identity of Unknowns
Unknown
A
B
C
D
E
Protein
Guess
Lipid
Monosaccharide
Identity
Real World Applications:
1. In the real world, when would performing these analysis tests for macromolecules be beneficial
to you and others?
2. Summarize what you have learned about the 4 macromolecules from this lab.
a. Carbohydrates
i. Monomer-monosaccharide
ii. Polymer-polysaccharide
b. Proteins
c.
Lipids
d. Nucleic acids