The foundation of every other unit. Water and its properties, the elements of life, and the four classes of biological macromolecules — carbohydrates, lipids, nucleic acids, and proteins. Master this and the rest of AP Bio gets a lot easier.
Six ways to master Unit 1 — pick whichever fits how you like to study.
Seven topics from the College Board CED, in order.
Unit 1 is the chemical foundation for the rest of AP Biology. You'll learn why water is so unusual for a small molecule — and why those properties (high specific heat, cohesion, surface tension) are exactly what makes life on Earth possible. You'll also meet the four classes of biological macromolecules and learn the basic rule that drives everything that follows: structure determines function.
This unit is roughly 8–11% of the AP Bio exam and takes about 9–11 class periods. It's not the most heavily weighted unit, but every other unit assumes you've mastered it. If you can't explain the difference between a phospholipid and a triglyceride here, Unit 2 (membranes) and Unit 4 (signaling) will be much harder.
The College Board ties Unit 1 to three of the four Big Ideas: