Unit 2: SMELLS Molecular Structure and Properties Living By Chemistry Unit 2: SMELLS Molecular Structure and Properties

Section IV: Molecules in the Body Lesson 20 Mirror, Mirror Lesson 21 Protein Origami Lesson 22 Who Nose?

Lesson 20: Mirror, Mirror Mirror-Image Isomers

ChemCatalyst Which of these objects looks identical in a mirror? Explain any differences. 1. glove 2. barbell 3. spring 4. tetrahedron

Key Question What are mirror-image isomers?

You will be able to: recognize mirror-image molecular structures explain what it means for molecules to be superimposable understand why mirror-image isomers have different properties

Prepare for the Activity Work in groups of four.

Discussion Notes Mirror-image molecules that cannot be superimposed on each other are called mirror-image isomers. Tetrahedral molecules in which four different atoms or groups are attached to a carbon atom always have mirror-image isomers.

Discussion Notes (cont.) The mirror-image isomers D-carvone and L-carvone have different smells. The mirror-image isomers have a “handedness.”

Wrap Up What are mirror-image isomers? Molecules that are not identical to their mirror image are called mirror-image isomers. Mirror-image isomers have a “handedness,” just like a right hand and a left hand. Mirror-image isomers can have different properties, including smell. Molecules that have at least one carbon atom with four different atoms or groups attached to it have a mirror-image isomer.

Check-in Which of these molecules will have a mirror-image isomer? Explain your reasoning. A. CF4 B. CHF3 C. C(CH3)4

Lesson 21: Protein Origami Amino Acids and Proteins

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.

Key Question What is a receptor site made of?

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

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.

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.

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.

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

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

Lesson 22: Who Nose? Unit Review

ChemCatalyst Name three items that might be on an exam covering the entire Smells Unit. Compose a question that could be included on the exam.

Key Question How is smell related to molecular structure and properties?

You will be able to: ask clarifying questions regarding concepts covered in this unit create a list of topics and concepts to study for an upcoming exam

Prepare for the Activity Work in pairs.

Discussion Notes The methyl salicylate molecule has structural features of both a minty molecule and a sweet molecule.

Check-in Would compounds made of either of these molecules have a smell? If so, try to predict what the smell would be. Explain your reasoning.