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 you molecule cards. What do they all have in common?
2. What differences do they have?
3. Classify them by putting them into piles and describe each pile.
Part 2: Interpreting Molecular Structure
4. Sort out all cards that contain nitrogen (N). Take this pile and sort out those that also contain
phosphors (P). How many cards do you have that contain both nitrogen and phosphorous?
Group 1: Nucleic Acids
5. Nucleic acids include RNA (ribonucleic acid) and DNA (deoxyribonucleic acid). Where is
DNA found?
6. What is DNA’s function for the cell?
7. Each nucleic acid contains three parts: a nitrogenous base, a five carbon sugar and a phosphate
group. Draw the three parts on your paper:
8. Which of the CHNOPS elements are found in nucleic acids?
9. List 2 differences between your nucleic acid cards.
Group 2: Amino Acids – building blocks of proteins
10. Proteins are molecules that play many important roles in the body; muscle structure, hormones,
antibodies, hemoglobin for carrying oxygen, transport proteins for carrying molecules across
cell membranes, 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. Draw an amino acid from your cards on your lab. Circle the amino group and put a
square around the carboxyl group.
11. How many amino acids do you have in your set?
12. Which of the CHNOPS elements are contained in ALL amino acids?
Group 3: Sugars – building blocks of carbohydrates
13. Sugars are literally hydrates of carbon, having the general formula “Cn(H2O) n. Sugars are
burned “oxidized” to release energy in what cellular process?
14. If n=6, how many carbon atoms are there? How many hydrogen atoms are there? How many
oxygen atoms are there?
15. Take your non-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?
16. What are the two forms of sugars?
17. Which of the CHNOPS elements are found in sugars?
18. 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?
Group 4: Lipids – contain 2 subgroups – fatty acids and steroids
Subgroup 1: Fatty Acids – building blocks of oils and fats
19. Fatty acids are long chains with a carboxyl group at one end and have an absence of oxygen in
the carboxyl group. How many fatty acids did you find?
20. 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 did
you find?
Subgroup 2: Steroids
If you have three remaining cards, you have been successful in classifying these molecules. These three
cards are steroids which are part of the cell membrane and used as chemical messengers.
21. Which CHNOPS elements are found in lipids?
Fill in the table:
Group
Monomer
Polymer
CHNOPS
Elements
Characteristics
Cellular Function
Nucleic Acids
Amino Acids
Sugars
Lipids: Fatty Acids
Lipids: Steroids
Conclusion: (Write 4-5 sentences summarizing the patterns you see as a result of classifying these molecules)