Name___________________________
Date___________ Period___________
Classifying Organic Molecules
Problem: What are living things made of? There may be as many as 10,000 different
kinds of molecules in living things. But are there a few common patterns?
Part 1: Classifying
1. Look at your molecule cards. What do they all have in common?
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2. What differences do they have?
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3. What are the 4 categories of organic molecules?
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Part 2: Interpreting Molecular Structure
4. Sort out all cards that contain nitrogen (N) into a “nitrogen” pile. Take this pile
and sort out those that also contain phosphorus (P). How many cards do you have
that contain both nitrogen and phosphorus? ___________
Group 1: Nucleotides
5. Nucleotides combine to form nucleic acids including DNA (deoxyribonucleic
acid), RNA (ribonucleic acid), and ATP (adenosine triphosphate). Where is DNA
found? _____________________
6. What is DNA’s function for the cell? ___________________________________
7. What is RNA’s function for the cell? ___________________________________
8. What is ATP’s function for the cell? ___________________________________
9. Each nucleotide contains three parts; a nitrogenous base, a five carbon sugar, and
a phosphate group. Circle and label the three parts below:
10. Which of the CHNOP elements are found in nucleic acids? _________________
11. List 2 differences between your nucleotide cards. ________________________
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Group 2: Amino Acids
12. Amino acids are the building blocks of proteins. Proteins are molecules that play
many important roles in the body; muscle structure, hormones, antibodies,
hemoglobin for carrying oxygen, transport proteins for carryin molecules across
the cell membrane, chemical messengers in the nervous system, and enzymes to
control chemical reactions. Each amino acid contains an amino group: NH3 and a
carboxyl group: COO or COOH. Label both, circle the amino group and put a
square around the carboxyl group.
13. Find the cards with an amino group and a carboxyl group. How many amino
acids do you have in your set? ________________
14. Which of the CHNOP elements are contained in ALL amino acids?___________
There should be 9 other cards left over in your “nitrogen” pile. Set these aside, we
will come back to them later.
Group 3: Sugars
15. Sugars are the building blocks of Carbohydrates. They are hydrates of carbon,
having the general formula “Cn(H2O)n. Sugars are burned “oxidized” to release
energy in what cellular process? _______________________________________
16. If n = 6, how many carbons are there? __________ How many hydrogens?
_________ How many oxygens? ___________
17. Take your “no nitrogen” pile and sort out those cards that have OH attached to
most carbons. Be aware that organic chemists use many shortcuts in drawing
complex molecules. They often do not include the letter C for carbon in ring
structures. How many cards did you find? ______________
18. What are the two forms of sugars? _____________________________________
19. Which of the CHNOP elements are found in sugars? _______________________
20. Sugars can be joined together in long chains to form large molecules called starch,
cellulose, and glycogen. Starch and glycogen are easily broken down into sugars
for energy. Cellulose, on the other hand, which is made in plants, can be broken
down only by a few organisms in the world (primarily the bacteria in the guts of
termites). What happens to the cellulose (fiber) you eat?
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Group 4: Lipids
21. Fatty acids are monomers of lipids. They are long chains with a carboxyl group at
one end and have an absence of oxygen except in the carboxyl group. How many
fatty acids did you find? _______________
22. Fatty acids that contain no double bonds between carbons are saturated. An
unsaturated fatty acid contains one or more double bonds between carbons. How
many saturated fatty acids do you have? __________ Unsaturated? __________
23. To form a lipid at least one fatty acid must bind to what other monomer?
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24. These lipids form the cell ____________________________.
25. If you have three remaining cards in the “no nitrogen” pile you have been
successful in classifying molecules. These three cards are steroids which are used
as chemical messengers throughout the body. Which CHNOP elements are found
in lipids? _____________________
There are still 9 cards left in your nitrogen pile. Those cards are not polymers or
monomers. See if you can figure out which molecules these are. Label the back of
all the molecule cards. Quiz your lab members.
Organize your information on this table:
Monomer
Polymer
Elements
Examples
Cellular
Function
Nucleotides
Amino Acids
Monosaccharide
Glycerol & Fatty
Acids
26. Write a paragraph explaining the similarities and differences between the organic
molecules. Include information on their structure and how it relates to their
function.
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