This document provides an overview of biochemistry and the four major macromolecules that make up living organisms: carbohydrates, lipids, proteins, and nucleic acids. It describes the basic composition and properties of each macromolecule, including that carbohydrates contain carbon, hydrogen, and oxygen and provide energy; lipids contain carbon, hydrogen, and oxygen and are used to store energy and provide structure; proteins contain carbon, hydrogen, nitrogen, and oxygen and serve as the building blocks for tissues and enzymes; and nucleic acids contain genetic information essential for life. Each macromolecule is composed of smaller monomers that polymerize to form the larger macromolecule.