Classifying organic molecules
Interpreting Molecular Structure
1. Sort out all cards that contain nitrogen (N). 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: Nucleic Acids
2. Nucleic acids include RNA (ribonucleic acid) and DNA (deoxyribonucleic acid). Where is
DNA found?
3. What is DNA’s function for the cell?
4. Each nucleic acid contains three parts: a nitrogenous base, a five carbon sugar and a
phosphate group. Draw the three parts on your paper:
5. Which of the CHNOPS elements are found in nucleic acids?
6. List 2 differences between your nucleic acid cards.
a.
b.
Group 2: Amino Acids – building blocks of proteins
7. 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.
8. How many amino acids do you have in your set?
9. Which of the CHNOPS elements are contained in ALL amino acids?
Group 3: Sugars – building blocks of carbohydrates
10. Sugars are literally hydrates of carbon, having the general formula “Cn(H2O) n”. Sugars
are burned “oxidized” to release energy in what cellular process?
11. If n=6 in formula Cn(H2O) n, how many carbon atoms are there?
How many hydrogen atoms are there?
How many oxygen atoms are there?
12. 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?
13. What are the two forms of sugars?
14. Which of the CHNOPS elements are found in sugars?
15. 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
16. 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?
17. 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.
18. Which CHNOPS elements are found in lipids?
SUMMARY:
Group
Combine to
Form
Elements
Characteristics
Nucleic Acids
Amino Acids
Sugars
Lipids: Fatty
Acids
Lipids: Steroids
Conclusion: (Write 3-5 sentences summarizing what you learned in this lab)
Cellular
Function