1. Worked Example 28.1 Classifying Hormones Based on Structure
Classify the following hormones as an amino acid derivative, a polypeptide, or a steroid.
Analysis
Hormones that are amino acid derivatives are recognized by the presence of amino groups. Those that are polypeptides are composed of amino acids. Steroids are recognizable by their distinctive four-ring structures.
Solution
Compound (a) is a steroid, (b) is an amino acid derivative, and (c) is a polypeptide.

2. Worked Example 28.2 Predicting Biological Activity Based on Structure
The relationship between the structure of a molecule and its biochemical function is an essential area of study in biochemistry and the design of drugs. Terfenadine (Seldane®) was one of the first of the new generation of “nondrowsy” antihistamines (it was removed from the market due to potential heart toxicity). Based solely on what you have learned so far, suggest which of its structural features make it an antihistamine.
Analysis
From Section 28.8, we see that members of the antihistamine family have in common the general structure shown here: an X group (usually a CH) to which two aromatic groups (noted as aryl in the drawing) are attached. The X is also attached to a disubstituted nitrogen by a carbon chain:

3. Worked Example 28.2 Predicting Biological Activity Based on Structure
Continued
Solution
Since terfenadine contains the same basic structure as a general antihistamine, its biological function should be similar.