Chapter 25 is one that you do not need to know in detail for this class. It is a very interesting and important part of chemistry and biology, but it is not covered on the AP exam in much detail. The study guide you have covers this chapter very well in topic 21.
Make sure you have an understanding of the following concepts-
Alkenes and Alkynes- watch unsaturated hydrocarbon video above
Organic Chemistry video- Select the one on Carbon at the bottom if it takes you to the main menu. Worksheet
Home work problems- 7, 8, 23, 17, 27, 35, 43 (these are new book updated)