Chem 336 - Spring 1999 - Organic Chemistry III
Portland State University - Dr. Carl C. Wamser

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Chapter 24 Quiz Answers

1. (5 points) D-Arabinose is the C-2 epimer of D-ribose. Write out its structure in an open-chain form, in an alpha-furanose form, and in a beta-pyranose form.

2. (3 points) Is the sugar shown below a reducing sugar? YES

Describe its structure relative to beta-D-glucose.

It is beta, and differs from D-glucose in that C-2 is deoxy and C-3 is the opposite stereochemistry of glucose.

3. (2 points) Describe (in words) the differences between starch and cellulose in terms of the bonding between monomer units and the structure of the polymer chains.

Starches use D-glucose joined alpha-1,4 and cellulose uses D-glucose joined beta-1,4. Starches tend to form a helical chain, while cellulose forms strands and sheets with strong H-bonding.