Chapter 9 Summary

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Archie McPhee and Company

CHAPTER 9

Molecules in the Body

SUMMARY

KEY TERMS

mirror-image isomer

amino acid

peptide bond (amide bond)

protein

Smells Update

Receptor sites exist throughout living systems. They serve as the mechanism for triggering many biological responses and processes, including smell. Receptor sites can be very specific, allowing only certain molecules to dock. So, the molecular structure of the receptor site is important. Some molecules have mirror-image isomers that have different properties, including smell. Amino acid molecules exist as mirror-image isomers. Amino acids combine to form a vast array of proteins, including those that make up receptor sites.

REVIEW EXERCISES

Question 9.1

1. How do you determine if two molecular models represent mirror-image isomers?

Question 9.2

2. Draw the structural formula for these molecules. Which have mirror-image isomers? Explain your reasoning.

  1. CBrClFH

  2. CH4

  3. CH2Cl2

Question 9.3

3. Explain how you could use your feet to show that the “handedness” of a molecule can determine if it fits into a receptor site.

Question 9.4

4. What are amino acids and what purpose do they serve in your body?

Question 9.5

5. Using the receptor site model, explain how a person can smell L-carvone but not its mirror-image isomer D-carvone.