1. Living By Chemistry SECOND EDITION
Unit 2: SMELLS
Molecular Structure and Properties

2. Lesson 48: Protein Origami
Amino Acids and Proteins

3. ChemCatalyst The mirror-image isomers of carvone are shown.
1. Explain how the receptor sites for D-carvone and L-carvone might be different from each other.
2. Sketch receptor sites for D-carvone and L-carvone.
Assume that the
polar side (the side
with the oxygen
atom) attaches
to the receptor
site.

4. Key Question
What is a receptor site made of?

5. You will be able to:
explain that protein molecules are chains of amino acid molecules
understand that the smell receptor sites are protein chains folded to form a receptor of a specific shape
explain the “handedness” of a smell receptor site

6. Prepare for the Activity
Work in groups of four.
Amino acid: A molecule with a carboxyl functional group and an amine functional group.
Protein: A large molecule consisting of amino acids bonded together.

7. Discussion Notes
Amino acids are molecules with a carboxyl group, COOH, and an amine group, NH2.
Amino acids can link together to form long chains called proteins.
Protein molecules fold to form pockets because of attractions between the R groups on different amino acids in the chain.

8. Wrap Up What is a receptor site made of?
Amino acids are molecules with a carboxyl group, COOH, and an amine group, NH2.
Amino acids all have mirror-image isomers. Only left-handed amino acid molecules function in the human body.
The carboxyl group from one amino acid can link with the amine group of another amino acid forming a peptide bond.

9. Wrap Up (cont.)
Proteins are long chains of amino acids linked together.
Protein molecules can fold to form smell receptor sites.

10. Check-In
Name two concepts from the Smells Unit that were used today to help you understand proteins.