- The production patterns of biological energy are divided into substrate-level phosphorylation (see Chapter 7), oxidative phosphorylation (respiration) and photophosphorylation (photosynthesis) as discussed in this chapter.
- In respiration and photosynthesis, through the convergence of a series of oxidation-reduction reactions into a common electron transport chain, all energy is replaced with the concentration gradient of H+ (electrochemical potential), and common F-ATP synthase synthesizes ATP using the electrochemical potential of H+.
- The respiration chain, the electron transport chain in photosynthesis and ATP synthase act as protein complexes incorporated into the biological membrane. These complexes react differently from many enzymes in aqueous solution, and have been studied in detail as typical examples of life’s complex systems.
- Energy changes in various reactions (free energy change (ΔG˚’), changes in oxidation-reduction potential (ΔE˚’), changes in the electrochemical potential of H+ (ΔμH+) and the formation and dissociation of ATP high-energy phosphate bonds) can be understood uniformly as being interconvertible.
- In respiration and photosynthesis, a mechanism exists to maintain a state of high energy by regulating ATP production and supply in response to ATP utilization and environmental changes. This mechanism is known as homeostasis.
- Biological systems can function autonomously because a high-energy state is maintained within cells.