Paul Andersen introduces the concept of bioenergetics. He explains how living organisms utilize free energy in the Universe. He begins with a brief discussion of thermodynamics and Gibbs free energy. He then explains how reactions can be exergonic or endergonic. He also introduces the concepts of photosynthesis and cellular respiration.

Paul Andersen describes how free energy is used by organisms to grow, maintain order, and reproduce. A brief discussion of the first and second law of thermodynamics is also included. Disruptions in the amount of free energy can cause death and disruptions to populations, communities, and ecosystems.

Paul Andersen attempts to explain Gibbs Free Energy. He begins by using three spontaneous reactions to explain how a change in enthalpy, entropy and temperature can affect the free energy of a system. He then applies this concept to cellular respiration and photosynthesis.