Bioenergetics deals with the very first energy transformation steps performed by living cells. Increased dissipation is the major effect of processing external energy packages. Enzyme-supported charge separation is the minor but essential outcome for maintaining life. These two events run together as driving-driven processes. The book explores the usefulness of dissecting the entropy production of enzymes involved in cellular defenses, fermentation, respiration, and photosynthesis, assuming that tightly regulated dissipation is the hallmark of life. This fresh outlook about the essence of life and bioenergetics is in accord with the evolution-coupling hypothesis: biological evolution accelerates the universe's thermodynamic evolution.