AP Biology Unit 1: Chemistry of Life

What Unit 1 covers

Unit 1 is the chemistry the rest of the course rests on. It starts with water: how its polarity and hydrogen bonding give it cohesion, adhesion, surface tension and a high specific heat. Then come the elements living things are built from and the four kinds of biological macromolecules (carbohydrates, lipids, proteins and nucleic acids): how monomers join by dehydration synthesis and split by hydrolysis, and how a molecule's structure decides what it does, from protein folding to the antiparallel strands of DNA.

Where students slip

• Hydrogen bonds in water form between molecules. The bonds inside a water molecule are polar covalent.
• Dehydration synthesis builds polymers and gives off water; hydrolysis uses water to break them apart. Under time pressure students swap the two.
• Secondary structure comes from hydrogen bonds along the polypeptide backbone; tertiary structure comes from interactions between R groups.
• The two strands of DNA are antiparallel: one runs 5′ to 3′, its partner 3′ to 5′.